CWE-22
Allowed-with-ReviewImproper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Abstraction: Base · Status: Stable
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
13217 vulnerabilities reference this CWE, most recent first.
GHSA-RXFF-VR5R-8CJ5
Vulnerability from github – Published: 2024-08-12 18:35 – Updated: 2024-11-26 18:521. Impacted Products
Streamilt Open Source versions before 1.37.0.
2. Introduction
Snowflake Streamlit open source addressed a security vulnerability via the static file sharing feature. The vulnerability was patched on Jul 25, 2024, as part of Streamlit open source version 1.37.0. The vulnerability only affects Windows.
3. Path Traversal Vulnerability
3.1 Description
On May 12, 2024, Streamlit was informed via our bug bounty program about a path traversal vulnerability in the open source library. We fixed and merged a patch remediating the vulnerability on Jul 25, 2024. The issue was determined to be in the moderate severity range with a maximum CVSSv3 base score of 5.9
3.2 Scenarios and attack vector(s)
Users of hosted Streamlit app(s) on Windows were vulnerable to a path traversal vulnerability when the static file sharing feature is enabled. An attacker could utilize the vulnerability to leak the password hash of the Windows user running Streamlit.
3.3 Resolution
The vulnerability has been fixed in all Streamlit versions released since Jul 25, 2024. We recommend all users upgrade to Version 1.37.0.
4. Contact
Please contact security@snowflake.com if you have any questions regarding this advisory. If you discover a security vulnerability in one of our products or websites, please report the issue to HackerOne. For more information, please see our Vulnerability Disclosure Policy.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "streamlit"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.37.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2024-42474"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": true,
"github_reviewed_at": "2024-08-12T18:35:12Z",
"nvd_published_at": "2024-08-12T17:15:17Z",
"severity": "MODERATE"
},
"details": "### 1. Impacted Products\nStreamilt Open Source versions before 1.37.0.\n\n### 2. Introduction\nSnowflake Streamlit open source addressed a security vulnerability via the [static file sharing feature](https://docs.streamlit.io/develop/concepts/configuration/serving-static-files). The vulnerability was patched on Jul 25, 2024, as part of Streamlit open source version 1.37.0. The vulnerability only affects Windows.\n\n### 3. Path Traversal Vulnerability \n#### 3.1 Description\nOn May 12, 2024, Streamlit was informed via our bug bounty program about a path traversal vulnerability in the open source library. We fixed and merged a patch remediating the vulnerability on Jul 25, 2024. The issue was determined to be in the moderate severity range with a maximum CVSSv3 base score of [5.9](https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N)\n#### 3.2 Scenarios and attack vector(s)\nUsers of hosted Streamlit app(s) on Windows were vulnerable to a path traversal vulnerability when the [static file sharing feature](https://docs.streamlit.io/develop/concepts/configuration/serving-static-files) is enabled. An attacker could utilize the vulnerability to leak the password hash of the Windows user running Streamlit. \n#### 3.3 Resolution\nThe vulnerability has been fixed in all Streamlit versions released since Jul 25, 2024. We recommend all users upgrade to Version 1.37.0.\n\n### 4. Contact\nPlease contact security@snowflake.com if you have any questions regarding this advisory. If you discover a security vulnerability in one of our products or websites, please report the issue to HackerOne. For more information, please see our [Vulnerability Disclosure Policy](https://hackerone.com/snowflake?type=team).\n",
"id": "GHSA-rxff-vr5r-8cj5",
"modified": "2024-11-26T18:52:17Z",
"published": "2024-08-12T18:35:12Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/streamlit/streamlit/security/advisories/GHSA-rxff-vr5r-8cj5"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-42474"
},
{
"type": "WEB",
"url": "https://github.com/streamlit/streamlit/commit/3a639859cfdfba2187c81897d44a3e33825eb0a3"
},
{
"type": "WEB",
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/streamlit/PYSEC-2024-153.yaml"
},
{
"type": "PACKAGE",
"url": "https://github.com/streamlit/streamlit"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Path traveral in Streamlit on windows"
}
GHSA-RXGH-JVQ6-75F7
Vulnerability from github – Published: 2022-03-28 00:00 – Updated: 2022-04-05 00:00aaPanel v6.8.21 was discovered to be vulnerable to directory traversal. This vulnerability allows attackers to obtain the root user private SSH key(id_rsa).
{
"affected": [],
"aliases": [
"CVE-2022-26252"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2022-03-27T16:15:00Z",
"severity": "MODERATE"
},
"details": "aaPanel v6.8.21 was discovered to be vulnerable to directory traversal. This vulnerability allows attackers to obtain the root user private SSH key(id_rsa).",
"id": "GHSA-rxgh-jvq6-75f7",
"modified": "2022-04-05T00:00:58Z",
"published": "2022-03-28T00:00:20Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-26252"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/50780"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-RXHJ-4M44-96R4
Vulnerability from github – Published: 2026-06-26 22:59 – Updated: 2026-06-26 22:59Summary
pnpm's patch application pipeline (@pnpm/patch-package) performs no path validation on file paths extracted from .patch files. An attacker who contributes a malicious patch file via a pull request can write attacker-controlled content to or delete arbitrary files on the filesystem during pnpm install, as the user running the install. The diff --git header paths containing ../../ sequences traverse out of the package directory, and the traversal is difficult to catch in code review because patch file diff headers are opaque to most reviewers.
Vulnerability Details
During pnpm install, when a patchedDependencies entry is present in pnpm-workspace.yaml, pnpm reads the referenced .patch file and applies it via the embedded @pnpm/patch-package library. The applyPatchToDir function at patching/apply-patch/src/index.ts:12-13 calls process.chdir(opts.patchedDir), setting the working directory to the installed package location deep inside node_modules/.pnpm/.
The patch parser at @pnpm/patch-package/dist/patch/parse.js:88 extracts file paths from diff --git a/(.*?) b/(.*?) headers using a regex with no path sanitization. The executeEffects function in apply.js then operates on these unsanitized paths:
File write (apply.js:35-49):
case 'file creation': {
const eff = effect
fs.ensureDirSync(dirname(eff.path))
fs.writeFileSync(eff.path, fileContents, { mode: eff.mode })
break
}
File delete (apply.js:13-22):
case 'file deletion': {
const eff = effect
// TODO: integrity checks
if (!opts.dryRun) {
fs.unlinkSync(eff.path)
}
break
}
A path like ../../../../../../../../../../home/user/.ssh/authorized_keys in the patch header traverses out of the package directory to an arbitrary location.
Proof of Concept
# Write variant:
bash autofyn_audit/exploits/vuln6_patch_traversal_write/exploit.sh
# Result: PASS -- /tmp/vuln6_pwned created with attacker-controlled content
# Delete variant:
bash autofyn_audit/exploits/vuln7_patch_traversal_delete/exploit.sh
# Result: PASS -- /tmp/vuln7_target deleted by malicious patch
# Combined chain (delete + replace SSH authorized_keys):
bash autofyn_audit/exploits/chain2_patch_ssh_backdoor/exploit.sh
# Result: PASS -- authorized_keys replaced with attacker's public key
Impact
Arbitrary file write and delete as the user running pnpm install, limited to paths writable by that user. An attacker who submits a PR adding a .patch file and patchedDependencies config can target SSH authorized_keys, shell configuration, CI/CD files, or other writable files. Patch files may receive less review scrutiny than package.json changes because the ../ traversal sequences are in diff --git headers that look like patch metadata.
Suggested Remediation
Validate parsed patch file paths against the package root directory. Reject any path that resolves outside the patched package directory via path.resolve + prefix check. Alternatively, sanitize at parse time by rejecting paths containing .. components in parse.js.
Discovered by AutoFyn Full audit report: audit_report.md Exploit script: exploit.sh
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "pnpm"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "10.34.0"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "pnpm"
},
"ranges": [
{
"events": [
{
"introduced": "11.0.0"
},
{
"fixed": "11.4.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-50015"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-26T22:59:48Z",
"nvd_published_at": "2026-06-25T18:16:39Z",
"severity": "HIGH"
},
"details": "## Summary\n\npnpm\u0027s patch application pipeline (`@pnpm/patch-package`) performs no path validation on file paths extracted from `.patch` files. An attacker who contributes a malicious patch file via a pull request can write attacker-controlled content to or delete arbitrary files on the filesystem during `pnpm install`, as the user running the install. The `diff --git` header paths containing `../../` sequences traverse out of the package directory, and the traversal is difficult to catch in code review because patch file diff headers are opaque to most reviewers.\n\n## Vulnerability Details\n\nDuring `pnpm install`, when a `patchedDependencies` entry is present in `pnpm-workspace.yaml`, pnpm reads the referenced `.patch` file and applies it via the embedded `@pnpm/patch-package` library. The `applyPatchToDir` function at `patching/apply-patch/src/index.ts:12-13` calls `process.chdir(opts.patchedDir)`, setting the working directory to the installed package location deep inside `node_modules/.pnpm/`.\n\nThe patch parser at `@pnpm/patch-package/dist/patch/parse.js:88` extracts file paths from `diff --git a/(.*?) b/(.*?)` headers using a regex with no path sanitization. The `executeEffects` function in `apply.js` then operates on these unsanitized paths:\n\n**File write** (`apply.js:35-49`):\n```javascript\ncase \u0027file creation\u0027: {\n const eff = effect\n fs.ensureDirSync(dirname(eff.path))\n fs.writeFileSync(eff.path, fileContents, { mode: eff.mode })\n break\n}\n```\n\n**File delete** (`apply.js:13-22`):\n```javascript\ncase \u0027file deletion\u0027: {\n const eff = effect\n // TODO: integrity checks\n if (!opts.dryRun) {\n fs.unlinkSync(eff.path)\n }\n break\n}\n```\n\nA path like `../../../../../../../../../../home/user/.ssh/authorized_keys` in the patch header traverses out of the package directory to an arbitrary location.\n\n## Proof of Concept\n\n```bash\n# Write variant:\nbash autofyn_audit/exploits/vuln6_patch_traversal_write/exploit.sh\n# Result: PASS -- /tmp/vuln6_pwned created with attacker-controlled content\n\n# Delete variant:\nbash autofyn_audit/exploits/vuln7_patch_traversal_delete/exploit.sh\n# Result: PASS -- /tmp/vuln7_target deleted by malicious patch\n\n# Combined chain (delete + replace SSH authorized_keys):\nbash autofyn_audit/exploits/chain2_patch_ssh_backdoor/exploit.sh\n# Result: PASS -- authorized_keys replaced with attacker\u0027s public key\n```\n\n## Impact\n\nArbitrary file write and delete as the user running `pnpm install`, limited to paths writable by that user. An attacker who submits a PR adding a `.patch` file and `patchedDependencies` config can target SSH authorized_keys, shell configuration, CI/CD files, or other writable files. Patch files may receive less review scrutiny than `package.json` changes because the `../` traversal sequences are in `diff --git` headers that look like patch metadata.\n\n## Suggested Remediation\n\nValidate parsed patch file paths against the package root directory. Reject any path that resolves outside the patched package directory via `path.resolve` + prefix check. Alternatively, sanitize at parse time by rejecting paths containing `..` components in `parse.js`.\n\n---\n\n\u003e Discovered by [AutoFyn](https://github.com/SignalPilot-Labs/AutoFyn)\n\u003e Full audit report: [audit_report.md](https://github.com/tempcollab/pnpm/blob/main/autofyn_audit/audit_report.md)\n\u003e Exploit script: [exploit.sh](https://github.com/tempcollab/pnpm/blob/main/autofyn_audit/exploits/vuln6_patch_traversal_write/exploit.sh)",
"id": "GHSA-rxhj-4m44-96r4",
"modified": "2026-06-26T22:59:49Z",
"published": "2026-06-26T22:59:48Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/pnpm/pnpm/security/advisories/GHSA-rxhj-4m44-96r4"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50015"
},
{
"type": "PACKAGE",
"url": "https://github.com/pnpm/pnpm"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "pnpm Vulnerable to Arbitrary File Write/Delete via Malicious Patch File (Path Traversal)"
}
GHSA-RXJP-MFM9-W4WR
Vulnerability from github – Published: 2021-06-04 21:15 – Updated: 2024-09-20 15:30In Django 2.2 before 2.2.21, 3.1 before 3.1.9, and 3.2 before 3.2.1, MultiPartParser, UploadedFile, and FieldFile allowed directory traversal via uploaded files with suitably crafted file names.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "Django"
},
"ranges": [
{
"events": [
{
"introduced": "2.2"
},
{
"fixed": "2.2.21"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "PyPI",
"name": "Django"
},
"ranges": [
{
"events": [
{
"introduced": "3.0"
},
{
"fixed": "3.1.9"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "PyPI",
"name": "Django"
},
"ranges": [
{
"events": [
{
"introduced": "3.2"
},
{
"fixed": "3.2.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2021-31542"
],
"database_specific": {
"cwe_ids": [
"CWE-22",
"CWE-434"
],
"github_reviewed": true,
"github_reviewed_at": "2021-05-19T20:28:55Z",
"nvd_published_at": "2021-05-05T15:15:00Z",
"severity": "HIGH"
},
"details": "In Django 2.2 before 2.2.21, 3.1 before 3.1.9, and 3.2 before 3.2.1, MultiPartParser, UploadedFile, and FieldFile allowed directory traversal via uploaded files with suitably crafted file names.",
"id": "GHSA-rxjp-mfm9-w4wr",
"modified": "2024-09-20T15:30:29Z",
"published": "2021-06-04T21:15:56Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-31542"
},
{
"type": "WEB",
"url": "https://github.com/django/django/commit/04ac1624bdc2fa737188401757cf95ced122d26d"
},
{
"type": "WEB",
"url": "https://github.com/django/django/commit/25d84d64122c15050a0ee739e859f22ddab5ac48"
},
{
"type": "WEB",
"url": "https://github.com/django/django/commit/c98f446c188596d4ba6de71d1b77b4a6c5c2a007"
},
{
"type": "WEB",
"url": "https://www.djangoproject.com/weblog/2021/may/04/security-releases"
},
{
"type": "WEB",
"url": "https://security.netapp.com/advisory/ntap-20210618-0001"
},
{
"type": "WEB",
"url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZVKYPHR3TKR2ESWXBPOJEKRO2OSJRZUE"
},
{
"type": "WEB",
"url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/B4SQG2EAF4WCI2SLRL6XRDJ3RPK3ZRDV"
},
{
"type": "WEB",
"url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZVKYPHR3TKR2ESWXBPOJEKRO2OSJRZUE"
},
{
"type": "WEB",
"url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/B4SQG2EAF4WCI2SLRL6XRDJ3RPK3ZRDV"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2021/05/msg00005.html"
},
{
"type": "WEB",
"url": "https://groups.google.com/forum/#%21forum/django-announce"
},
{
"type": "WEB",
"url": "https://groups.google.com/forum/#!forum/django-announce"
},
{
"type": "WEB",
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/django/PYSEC-2021-7.yaml"
},
{
"type": "PACKAGE",
"url": "https://github.com/django/django"
},
{
"type": "ADVISORY",
"url": "https://github.com/advisories/GHSA-rxjp-mfm9-w4wr"
},
{
"type": "WEB",
"url": "https://docs.djangoproject.com/en/3.2/releases/security"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2021/05/04/3"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Path Traversal in Django"
}
GHSA-RXRJ-XHR7-FJQG
Vulnerability from github – Published: 2022-05-14 03:51 – Updated: 2022-05-14 03:51PHP Scripts Mall Professional Service Script allows remote attackers to obtain sensitive full-path information via the id parameter to admin/review_userwise.php.
{
"affected": [],
"aliases": [
"CVE-2017-17924"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2017-12-27T17:08:00Z",
"severity": "MODERATE"
},
"details": "PHP Scripts Mall Professional Service Script allows remote attackers to obtain sensitive full-path information via the id parameter to admin/review_userwise.php.",
"id": "GHSA-rxrj-xhr7-fjqg",
"modified": "2022-05-14T03:51:16Z",
"published": "2022-05-14T03:51:16Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2017-17924"
},
{
"type": "WEB",
"url": "https://github.com/d4wner/Vulnerabilities-Report/blob/master/Professional-Service-Script.md"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-RXVQ-9432-RG42
Vulnerability from github – Published: 2022-05-17 02:42 – Updated: 2022-05-17 02:42A directory traversal vulnerability exists in core\admin\ajax\developer\extensions\file-browser.php in BigTree CMS through 4.2.18 on Windows, allowing attackers to read arbitrary files via ..\ sequences in the directory parameter.
{
"affected": [],
"aliases": [
"CVE-2017-9428"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2017-06-04T23:29:00Z",
"severity": "HIGH"
},
"details": "A directory traversal vulnerability exists in core\\admin\\ajax\\developer\\extensions\\file-browser.php in BigTree CMS through 4.2.18 on Windows, allowing attackers to read arbitrary files via ..\\ sequences in the directory parameter.",
"id": "GHSA-rxvq-9432-rg42",
"modified": "2022-05-17T02:42:44Z",
"published": "2022-05-17T02:42:44Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2017-9428"
},
{
"type": "WEB",
"url": "https://github.com/bigtreecms/BigTree-CMS/issues/289"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-RXW2-PC8J-VXWM
Vulnerability from github – Published: 2026-07-02 20:38 – Updated: 2026-07-02 20:38Summary
fast-mcp-telegram validates HTTP Bearer tokens by joining the raw token string into a session-file path. The verifier rejects the exact reserved token telegram, but it does not reject path separators or normalize the path before checking whether the session file exists. A remote HTTP client can therefore authenticate as the default legacy session with a token such as ../fast-mcp-telegram/telegram when the documented default session file ~/.config/fast-mcp-telegram/telegram.session exists.
This bypasses the reserved session name control that is intended to prevent HTTP multi-user sessions from colliding with the default stdio or legacy account. With account-prefixed MCP tools enabled, the attacker still sees and calls the prefixed tools for the default account, so the prefix middleware does not stop the session selection bypass.
Impact
An unauthenticated network client can access the Telegram account represented by the default telegram.session file without knowing a generated bearer token, if that legacy or default session file is present on a server running HTTP auth. The attacker can then call Telegram MCP tools as that account, including message reading, message sending, MTProto API calls, and attachment-producing tool surfaces available to the session.
Technical details
SessionFileTokenVerifier.verify_token() strips whitespace and rejects exact reserved names:
if token.lower() in RESERVED_SESSION_NAMES:
return None
It then appends .session to the raw token and checks the resulting path:
session_path = self._session_directory / f"{token}.session"
if not session_path.is_file():
return None
No check rejects /, \\, .., absolute paths, or resolved paths outside the configured session directory. The session client path is built the same way in src/client/connection.py:
session_path = SESSION_DIR / f"{token}.session"
client = await _build_telegram_client_for_token(session_path, token)
With the default session directory, the token ../fast-mcp-telegram/telegram resolves as follows:
~/.config/fast-mcp-telegram/../fast-mcp-telegram/telegram.session
= ~/.config/fast-mcp-telegram/telegram.session
The exact token telegram is denied, but the traversal alias reaches the same file and is accepted. This is especially important because telegram is the documented default session_name, and the security documentation says reserved names are blocked to prevent conflicts with stdio and HTTP no-auth sessions.
The vulnerable code is present on current master commit 167ab705f1cd09b21e85c370570471fe75a4f8c9 and in release tag 0.19.0 commit 77bdf6d7e5c6a84d87acc423db613e6c6ba30094.
Reproduction
The following proof uses stub session files and stub Telegram clients, so it does not need real Telegram credentials. It validates the auth decision and the eventual session path used by the client builder.
Run on current master:
git clone https://github.com/leshchenko1979/fast-mcp-telegram.git
cd fast-mcp-telegram
python validation_token_traversal.py
The local proof script created for validation is attached below for reference:
# High-level proof outline
# 1. Create a temporary session directory containing telegram.session and a random token session.
# 2. Instantiate SessionFileTokenVerifier with that directory.
# 3. Verify denied controls: token `telegram` is rejected, and a traversal token to a missing file is rejected.
# 4. Verify allowed control: a normal random token with a matching session file is accepted.
# 5. Verify bypass: token `../fast-mcp-telegram/telegram` is accepted and the client builder receives the default telegram.session path.
# 6. Verify prefix behavior: account-prefixed tools are listed for the traversal-authenticated default account, a prefixed call reaches send_message, and an unprefixed call is still denied.
Key controls from the current-master run:
{
"reserved_default_token_denied": true,
"normal_random_token_allowed": true,
"missing_traversal_token_denied": true,
"traversal_alias_to_reserved_default_allowed": true,
"traversal_access_token_value": "../fast-mcp-telegram/telegram",
"client_builder_used_default_session_file": true,
"prefixed_tool_listed_for_traversal_token": "defaultalice_send_message",
"prefixed_tool_call_reached_handler_as": "send_message",
"unprefixed_tool_call_denied_when_prefix_resolved": true
}
Interpretation:
- Denied control: the exact reserved token
telegramis rejected. - Allowed control: a normal random session token is accepted when its matching session file exists.
- Denied control: a traversal token pointing to a missing file is rejected.
- Bypass:
../fast-mcp-telegram/telegramauthenticates and the client builder receives the resolved default session path. - Prefix control: once authenticated through the traversal token, account-prefixed tools are listed and a prefixed
tools/callreaches the internalsend_messagehandler. An unprefixed call is rejected when the prefix resolves, so the confirmed bug is the session selection and authentication bypass, not a missing-prefix execution bypass.
Why this crosses the auth boundary
A production HTTP auth deployment is expected to require high-entropy per-session bearer tokens. Reserved names are explicitly blocked because common names such as telegram can collide with the default session. The traversal alias turns the public token namespace back into a filesystem namespace and bypasses that reserved-name policy.
The account-prefix middleware is downstream of authentication. It labels tools based on the resolved Telegram account for the token that was accepted. Because the traversal token is accepted as a valid FastMCP AccessToken, the middleware correctly exposes the default account's prefixed tools to the attacker. It cannot recover the lost authentication boundary.
Remediation
Reject bearer tokens that are not strict opaque token identifiers before using them in file paths. Recommended checks:
- Accept only a safe token alphabet, for example
^[A-Za-z0-9_-]{32,128}$, matching generated URL-safe base64 tokens. - Reject
/,\\,.,.., empty segments, and absolute paths for both header auth and URL auth. - Resolve the final session path and require it to remain directly under the configured session directory:
session_dir = self._session_directory.resolve()
session_path = (session_dir / f"{token}.session").resolve()
if session_path.parent != session_dir:
return None
- Apply the same validation in
SessionFileTokenVerifier, URL auth middleware, setup flows, cleanup code, and any code that opens session files by token. - Add regression tests for exact reserved names, traversal aliases such as
../fast-mcp-telegram/telegram, absolute paths, URL-encoded traversal if any route decodes path components, Windows separators, and normal generated tokens.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.19.0"
},
"package": {
"ecosystem": "PyPI",
"name": "fast-mcp-telegram"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.19.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-52830"
],
"database_specific": {
"cwe_ids": [
"CWE-22",
"CWE-287"
],
"github_reviewed": true,
"github_reviewed_at": "2026-07-02T20:38:50Z",
"nvd_published_at": null,
"severity": "CRITICAL"
},
"details": "## Summary\n\nfast-mcp-telegram validates HTTP Bearer tokens by joining the raw token string into a session-file path. The verifier rejects the exact reserved token `telegram`, but it does not reject path separators or normalize the path before checking whether the session file exists. A remote HTTP client can therefore authenticate as the default legacy session with a token such as `../fast-mcp-telegram/telegram` when the documented default session file `~/.config/fast-mcp-telegram/telegram.session` exists.\n\nThis bypasses the reserved session name control that is intended to prevent HTTP multi-user sessions from colliding with the default stdio or legacy account. With account-prefixed MCP tools enabled, the attacker still sees and calls the prefixed tools for the default account, so the prefix middleware does not stop the session selection bypass.\n\n## Impact\n\nAn unauthenticated network client can access the Telegram account represented by the default `telegram.session` file without knowing a generated bearer token, if that legacy or default session file is present on a server running HTTP auth. The attacker can then call Telegram MCP tools as that account, including message reading, message sending, MTProto API calls, and attachment-producing tool surfaces available to the session.\n\n## Technical details\n\n`SessionFileTokenVerifier.verify_token()` strips whitespace and rejects exact reserved names:\n\n```python\nif token.lower() in RESERVED_SESSION_NAMES:\n return None\n```\n\nIt then appends `.session` to the raw token and checks the resulting path:\n\n```python\nsession_path = self._session_directory / f\"{token}.session\"\nif not session_path.is_file():\n return None\n```\n\nNo check rejects `/`, `\\\\`, `..`, absolute paths, or resolved paths outside the configured session directory. The session client path is built the same way in `src/client/connection.py`:\n\n```python\nsession_path = SESSION_DIR / f\"{token}.session\"\nclient = await _build_telegram_client_for_token(session_path, token)\n```\n\nWith the default session directory, the token `../fast-mcp-telegram/telegram` resolves as follows:\n\n```text\n~/.config/fast-mcp-telegram/../fast-mcp-telegram/telegram.session\n= ~/.config/fast-mcp-telegram/telegram.session\n```\n\nThe exact token `telegram` is denied, but the traversal alias reaches the same file and is accepted. This is especially important because `telegram` is the documented default `session_name`, and the security documentation says reserved names are blocked to prevent conflicts with stdio and HTTP no-auth sessions.\n\nThe vulnerable code is present on current `master` commit `167ab705f1cd09b21e85c370570471fe75a4f8c9` and in release tag `0.19.0` commit `77bdf6d7e5c6a84d87acc423db613e6c6ba30094`.\n\n## Reproduction\n\nThe following proof uses stub session files and stub Telegram clients, so it does not need real Telegram credentials. It validates the auth decision and the eventual session path used by the client builder.\n\nRun on current master:\n\n```bash\ngit clone https://github.com/leshchenko1979/fast-mcp-telegram.git\ncd fast-mcp-telegram\npython validation_token_traversal.py\n```\n\nThe local proof script created for validation is attached below for reference:\n\n```python\n# High-level proof outline\n# 1. Create a temporary session directory containing telegram.session and a random token session.\n# 2. Instantiate SessionFileTokenVerifier with that directory.\n# 3. Verify denied controls: token `telegram` is rejected, and a traversal token to a missing file is rejected.\n# 4. Verify allowed control: a normal random token with a matching session file is accepted.\n# 5. Verify bypass: token `../fast-mcp-telegram/telegram` is accepted and the client builder receives the default telegram.session path.\n# 6. Verify prefix behavior: account-prefixed tools are listed for the traversal-authenticated default account, a prefixed call reaches send_message, and an unprefixed call is still denied.\n```\n\nKey controls from the current-master run:\n\n```json\n{\n \"reserved_default_token_denied\": true,\n \"normal_random_token_allowed\": true,\n \"missing_traversal_token_denied\": true,\n \"traversal_alias_to_reserved_default_allowed\": true,\n \"traversal_access_token_value\": \"../fast-mcp-telegram/telegram\",\n \"client_builder_used_default_session_file\": true,\n \"prefixed_tool_listed_for_traversal_token\": \"defaultalice_send_message\",\n \"prefixed_tool_call_reached_handler_as\": \"send_message\",\n \"unprefixed_tool_call_denied_when_prefix_resolved\": true\n}\n```\n\nInterpretation:\n\n1. Denied control: the exact reserved token `telegram` is rejected.\n2. Allowed control: a normal random session token is accepted when its matching session file exists.\n3. Denied control: a traversal token pointing to a missing file is rejected.\n4. Bypass: `../fast-mcp-telegram/telegram` authenticates and the client builder receives the resolved default session path.\n5. Prefix control: once authenticated through the traversal token, account-prefixed tools are listed and a prefixed `tools/call` reaches the internal `send_message` handler. An unprefixed call is rejected when the prefix resolves, so the confirmed bug is the session selection and authentication bypass, not a missing-prefix execution bypass.\n\n## Why this crosses the auth boundary\n\nA production HTTP auth deployment is expected to require high-entropy per-session bearer tokens. Reserved names are explicitly blocked because common names such as `telegram` can collide with the default session. The traversal alias turns the public token namespace back into a filesystem namespace and bypasses that reserved-name policy.\n\nThe account-prefix middleware is downstream of authentication. It labels tools based on the resolved Telegram account for the token that was accepted. Because the traversal token is accepted as a valid FastMCP `AccessToken`, the middleware correctly exposes the default account\u0027s prefixed tools to the attacker. It cannot recover the lost authentication boundary.\n\n## Remediation\n\nReject bearer tokens that are not strict opaque token identifiers before using them in file paths. Recommended checks:\n\n1. Accept only a safe token alphabet, for example `^[A-Za-z0-9_-]{32,128}$`, matching generated URL-safe base64 tokens.\n2. Reject `/`, `\\\\`, `.`, `..`, empty segments, and absolute paths for both header auth and URL auth.\n3. Resolve the final session path and require it to remain directly under the configured session directory:\n\n```python\nsession_dir = self._session_directory.resolve()\nsession_path = (session_dir / f\"{token}.session\").resolve()\nif session_path.parent != session_dir:\n return None\n```\n\n4. Apply the same validation in `SessionFileTokenVerifier`, URL auth middleware, setup flows, cleanup code, and any code that opens session files by token.\n5. Add regression tests for exact reserved names, traversal aliases such as `../fast-mcp-telegram/telegram`, absolute paths, URL-encoded traversal if any route decodes path components, Windows separators, and normal generated tokens.",
"id": "GHSA-rxw2-pc8j-vxwm",
"modified": "2026-07-02T20:38:50Z",
"published": "2026-07-02T20:38:50Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/leshchenko1979/fast-mcp-telegram/security/advisories/GHSA-rxw2-pc8j-vxwm"
},
{
"type": "PACKAGE",
"url": "https://github.com/leshchenko1979/fast-mcp-telegram"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L",
"type": "CVSS_V3"
}
],
"summary": "fast-mcp-telegram: Bearer token path traversal bypasses reserved Telegram session protection"
}
GHSA-RXW3-JM8W-C989
Vulnerability from github – Published: 2024-06-25 21:31 – Updated: 2024-08-21 15:30In WhatsUp Gold versions released before 2023.1.3, a path traversal vulnerability exists. A specially crafted unauthenticated HTTP request to AppProfileImport can lead can lead to information disclosure.
{
"affected": [],
"aliases": [
"CVE-2024-5017"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-06-25T21:16:01Z",
"severity": "MODERATE"
},
"details": "In WhatsUp Gold versions released before 2023.1.3, a path traversal vulnerability exists.\u00a0A specially crafted unauthenticated HTTP request\u00a0to AppProfileImport can lead can lead to information disclosure.",
"id": "GHSA-rxw3-jm8w-c989",
"modified": "2024-08-21T15:30:50Z",
"published": "2024-06-25T21:31:18Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-5017"
},
{
"type": "WEB",
"url": "https://community.progress.com/s/article/WhatsUp-Gold-Security-Bulletin-June-2024"
},
{
"type": "WEB",
"url": "https://www.progress.com/network-monitoring"
},
{
"type": "WEB",
"url": "https://www.talosintelligence.com/vulnerability_reports/TALOS-2024-1932"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-RXW5-Q35G-8PH9
Vulnerability from github – Published: 2022-05-24 16:45 – Updated: 2023-03-24 18:30A vulnerability in the web-based management interface of Cisco Prime Infrastructure and Cisco Evolved Programmable Network (EPN) Manager software could allow an authenticated, remote attacker to download and view files within the application that should be restricted. This vulnerability is due to improper sanitization of user-supplied input in HTTP request parameters that describe filenames. An attacker could exploit this vulnerability by using directory traversal techniques to submit a path to a desired file location. A successful exploit could allow the attacker to view application files that may contain sensitive information.
{
"affected": [],
"aliases": [
"CVE-2019-1819"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2019-05-16T01:29:00Z",
"severity": "MODERATE"
},
"details": "A vulnerability in the web-based management interface of Cisco Prime Infrastructure and Cisco Evolved Programmable Network (EPN) Manager software could allow an authenticated, remote attacker to download and view files within the application that should be restricted. This vulnerability is due to improper sanitization of user-supplied input in HTTP request parameters that describe filenames. An attacker could exploit this vulnerability by using directory traversal techniques to submit a path to a desired file location. A successful exploit could allow the attacker to view application files that may contain sensitive information.",
"id": "GHSA-rxw5-q35g-8ph9",
"modified": "2023-03-24T18:30:23Z",
"published": "2022-05-24T16:45:56Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-1819"
},
{
"type": "WEB",
"url": "https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190515-pi-pathtrav-1819"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/108351"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-RXXV-4H4G-975C
Vulnerability from github – Published: 2025-08-08 06:30 – Updated: 2025-08-08 06:30Powered BLUE Server versions 0.20130927 and prior contain a path traversal vulnerability. If this vulnerability is exploited, an arbitrary file in the affected product may be disclosed.
{
"affected": [],
"aliases": [
"CVE-2025-54959"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-08-08T05:15:32Z",
"severity": "MODERATE"
},
"details": "Powered BLUE Server versions 0.20130927 and prior contain a path traversal vulnerability. If this vulnerability is exploited, an arbitrary file in the affected product may be disclosed.",
"id": "GHSA-rxxv-4h4g-975c",
"modified": "2025-08-08T06:30:25Z",
"published": "2025-08-08T06:30:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-54959"
},
{
"type": "WEB",
"url": "https://jvn.jp/en/jp/JVN39636188"
},
{
"type": "WEB",
"url": "https://www.mubit.co.jp/sub/products/blue/pb-base-cloud-890.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
Mitigation MIT-5.1
Strategy: Input Validation
- Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434.
- Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.
Mitigation MIT-15
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Mitigation MIT-20.1
Strategy: Input Validation
- Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
- Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59). This includes:
- realpath() in C
- getCanonicalPath() in Java
- GetFullPath() in ASP.NET
- realpath() or abs_path() in Perl
- realpath() in PHP
Mitigation MIT-4
Strategy: Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482].
Mitigation MIT-29
Strategy: Firewall
Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].
Mitigation MIT-17
Strategy: Environment Hardening
Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.
Mitigation MIT-21.1
Strategy: Enforcement by Conversion
- When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
- For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt". Features such as the ESAPI AccessReferenceMap [REF-185] provide this capability.
Mitigation MIT-22
Strategy: Sandbox or Jail
- Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
- OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.
- This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.
- Be careful to avoid CWE-243 and other weaknesses related to jails.
Mitigation MIT-34
Strategy: Attack Surface Reduction
- Store library, include, and utility files outside of the web document root, if possible. Otherwise, store them in a separate directory and use the web server's access control capabilities to prevent attackers from directly requesting them. One common practice is to define a fixed constant in each calling program, then check for the existence of the constant in the library/include file; if the constant does not exist, then the file was directly requested, and it can exit immediately.
- This significantly reduces the chance of an attacker being able to bypass any protection mechanisms that are in the base program but not in the include files. It will also reduce the attack surface.
Mitigation MIT-39
- Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success.
- If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files.
- Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.
- In the context of path traversal, error messages which disclose path information can help attackers craft the appropriate attack strings to move through the file system hierarchy.
Mitigation MIT-16
Strategy: Environment Hardening
When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.
CAPEC-126: Path Traversal
An adversary uses path manipulation methods to exploit insufficient input validation of a target to obtain access to data that should be not be retrievable by ordinary well-formed requests. A typical variety of this attack involves specifying a path to a desired file together with dot-dot-slash characters, resulting in the file access API or function traversing out of the intended directory structure and into the root file system. By replacing or modifying the expected path information the access function or API retrieves the file desired by the attacker. These attacks either involve the attacker providing a complete path to a targeted file or using control characters (e.g. path separators (/ or \) and/or dots (.)) to reach desired directories or files.
CAPEC-64: Using Slashes and URL Encoding Combined to Bypass Validation Logic
This attack targets the encoding of the URL combined with the encoding of the slash characters. An attacker can take advantage of the multiple ways of encoding a URL and abuse the interpretation of the URL. A URL may contain special character that need special syntax handling in order to be interpreted. Special characters are represented using a percentage character followed by two digits representing the octet code of the original character (%HEX-CODE). For instance US-ASCII space character would be represented with %20. This is often referred as escaped ending or percent-encoding. Since the server decodes the URL from the requests, it may restrict the access to some URL paths by validating and filtering out the URL requests it received. An attacker will try to craft an URL with a sequence of special characters which once interpreted by the server will be equivalent to a forbidden URL. It can be difficult to protect against this attack since the URL can contain other format of encoding such as UTF-8 encoding, Unicode-encoding, etc.
CAPEC-76: Manipulating Web Input to File System Calls
An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.
CAPEC-78: Using Escaped Slashes in Alternate Encoding
This attack targets the use of the backslash in alternate encoding. An adversary can provide a backslash as a leading character and causes a parser to believe that the next character is special. This is called an escape. By using that trick, the adversary tries to exploit alternate ways to encode the same character which leads to filter problems and opens avenues to attack.
CAPEC-79: Using Slashes in Alternate Encoding
This attack targets the encoding of the Slash characters. An adversary would try to exploit common filtering problems related to the use of the slashes characters to gain access to resources on the target host. Directory-driven systems, such as file systems and databases, typically use the slash character to indicate traversal between directories or other container components. For murky historical reasons, PCs (and, as a result, Microsoft OSs) choose to use a backslash, whereas the UNIX world typically makes use of the forward slash. The schizophrenic result is that many MS-based systems are required to understand both forms of the slash. This gives the adversary many opportunities to discover and abuse a number of common filtering problems. The goal of this pattern is to discover server software that only applies filters to one version, but not the other.