CWE-73
AllowedExternal Control of File Name or Path
Abstraction: Base · Status: Draft
The product allows user input to control or influence paths or file names that are used in filesystem operations.
1060 vulnerabilities reference this CWE, most recent first.
GHSA-RMQ3-JW86-CMWM
Vulnerability from github – Published: 2026-08-04 00:34 – Updated: 2026-08-04 00:34External control of file name or path in Microsoft Edge for Android allows an unauthorized attacker to disclose information over a network.
{
"affected": [],
"aliases": [
"CVE-2026-65802"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-04T00:17:37Z",
"severity": "HIGH"
},
"details": "External control of file name or path in Microsoft Edge for Android allows an unauthorized attacker to disclose information over a network.",
"id": "GHSA-rmq3-jw86-cmwm",
"modified": "2026-08-04T00:34:54Z",
"published": "2026-08-04T00:34:54Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-65802"
},
{
"type": "WEB",
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-65802"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-RMQR-H98C-QG2M
Vulnerability from github – Published: 2026-05-15 21:31 – Updated: 2026-06-09 00:00Duplicate Advisory
This advisory has been withdrawn because it is a duplicate of GHSA-gh9p-q46p-57g2. This link is maintained to preserve external references.
Original Description
phpMyFAQ before 4.1.2 contains a path traversal vulnerability in Client::deleteClientFolder that allows admins with INSTANCE_DELETE permission to delete arbitrary directories. Attackers can submit traversal sequences like https://../../../ in the client URL parameter to recursively delete directories outside the intended clientFolder scope.
{
"affected": [
{
"package": {
"ecosystem": "Packagist",
"name": "phpMyFAQ/phpMyFAQ"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "4.1.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-21T21:12:39Z",
"nvd_published_at": "2026-05-15T19:17:01Z",
"severity": "HIGH"
},
"details": "### Duplicate Advisory\nThis advisory has been withdrawn because it is a duplicate of GHSA-gh9p-q46p-57g2. This link is maintained to preserve external references.\n\n### Original Description\nphpMyFAQ before 4.1.2 contains a path traversal vulnerability in Client::deleteClientFolder that allows admins with INSTANCE_DELETE permission to delete arbitrary directories. Attackers can submit traversal sequences like https://../../../\u003cpath\u003e in the client URL parameter to recursively delete directories outside the intended clientFolder scope.",
"id": "GHSA-rmqr-h98c-qg2m",
"modified": "2026-06-09T00:00:53Z",
"published": "2026-05-15T21:31:32Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/thorsten/phpMyFAQ/security/advisories/GHSA-gh9p-q46p-57g2"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45008"
},
{
"type": "PACKAGE",
"url": "https://github.com/thorsten/phpMyFAQ"
},
{
"type": "WEB",
"url": "https://www.vulncheck.com/advisories/phpmyfaq-path-traversal-in-client-deleteclientfolder-via-url-parameter"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:H/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"
}
],
"summary": "Duplicate Advisory: phpMyFAQ: Path traversal in Client::deleteClientFolder enables arbitrary directory deletion by non-super-admin admins",
"withdrawn": "2026-06-09T00:00:53Z"
}
GHSA-RPR2-8RVV-249V
Vulnerability from github – Published: 2026-07-14 18:32 – Updated: 2026-07-14 18:32External control of file name or path in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
{
"affected": [],
"aliases": [
"CVE-2026-50462"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-14T18:17:51Z",
"severity": "HIGH"
},
"details": "External control of file name or path in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.",
"id": "GHSA-rpr2-8rvv-249v",
"modified": "2026-07-14T18:32:25Z",
"published": "2026-07-14T18:32:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50462"
},
{
"type": "WEB",
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50462"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-RPW7-C5CP-V8VP
Vulnerability from github – Published: 2024-02-07 03:30 – Updated: 2026-04-20 18:31Leanote version 2.7.0 allows obtaining arbitrary local files. This is possible
because the application is vulnerable to LFR.
{
"affected": [],
"aliases": [
"CVE-2024-0849"
],
"database_specific": {
"cwe_ids": [
"CWE-20",
"CWE-22",
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-02-07T03:15:50Z",
"severity": "MODERATE"
},
"details": "Leanote version 2.7.0 allows obtaining arbitrary local files. This is possible\n\nbecause the application is vulnerable to LFR.",
"id": "GHSA-rpw7-c5cp-v8vp",
"modified": "2026-04-20T18:31:41Z",
"published": "2024-02-07T03:30:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-0849"
},
{
"type": "WEB",
"url": "https://fluidattacks.com/advisories/alesso"
},
{
"type": "WEB",
"url": "https://github.com/leanote/desktop-app"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-RQJ4-C9GX-XX38
Vulnerability from github – Published: 2025-11-01 09:30 – Updated: 2025-11-01 09:30The Import WP – Export and Import CSV and XML files to WordPress plugin for WordPress is vulnerable to Arbitrary File Read in all versions up to, and including, 2.14.16. This is due to the plugin's REST API endpoint accepting arbitrary absolute file paths without proper validation in the 'attach_file()' function when handling 'file_local' actions. This makes it possible for authenticated attackers, with administrator-level access and above, to read arbitrary files on the server's filesystem, including sensitive configuration files and system files via the 'local_url' parameter.
{
"affected": [],
"aliases": [
"CVE-2025-12137"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-11-01T07:15:35Z",
"severity": "MODERATE"
},
"details": "The Import WP \u2013 Export and Import CSV and XML files to WordPress plugin for WordPress is vulnerable to Arbitrary File Read in all versions up to, and including, 2.14.16. This is due to the plugin\u0027s REST API endpoint accepting arbitrary absolute file paths without proper validation in the \u0027attach_file()\u0027 function when handling \u0027file_local\u0027 actions. This makes it possible for authenticated attackers, with administrator-level access and above, to read arbitrary files on the server\u0027s filesystem, including sensitive configuration files and system files via the \u0027local_url\u0027 parameter.",
"id": "GHSA-rqj4-c9gx-xx38",
"modified": "2025-11-01T09:30:17Z",
"published": "2025-11-01T09:30:17Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-12137"
},
{
"type": "WEB",
"url": "https://github.com/importwp/importwp/commit/94cc524aa0c81be6463a9e8d154b00220e34709c"
},
{
"type": "WEB",
"url": "https://cwe.mitre.org/data/definitions/36.html"
},
{
"type": "WEB",
"url": "https://owasp.org/www-community/attacks/Path_Traversal"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/jc-importer/trunk/class/Common/Filesystem/Filesystem.php#L212"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/jc-importer/trunk/class/Common/Filesystem/Filesystem.php#L56"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/jc-importer/trunk/class/Common/Importer/ImporterManager.php#L435"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/jc-importer/trunk/class/Common/Rest/RestManager.php#L1079"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/changeset?sfp_email=\u0026sfph_mail=\u0026reponame=\u0026old=3387749%40jc-importer\u0026new=3387749%40jc-importer\u0026sfp_email=\u0026sfph_mail="
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/f10636ea-06aa-4186-a891-ed4bb0800c41?source=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-RR55-JP92-8WP2
Vulnerability from github – Published: 2026-08-19 19:15 – Updated: 2026-08-19 19:15Summary
claude-faf-mcp MCP tools accept a caller-controlled path argument and resolve it (~ expansion + path.resolve()) straight into a filesystem read/write without confining it to a trusted project directory. An absolute path or ../ traversal is resolved and used as-is, so the server process can be made to read — and, via the file tools, write — files outside the intended .faf project context. The only remaining limit is OS file permissions.
Affected tools
The shared getProjectPath() chokepoint (feeding the .faf tools) and the general-purpose faf_read / faf_write file tools resolved a caller path straight into a read/write with no confinement (denylist-only); an absolute path still reached home-directory secrets, and faf_write could write outside the project.
Impact
An MCP client — or an LLM prompt-injected via attacker-controlled content (a web page, README, ticket, or .faf) into issuing a tool call — can read any file the server process can read: SSH keys (~/.ssh/id_rsa), cloud credentials (~/.aws/credentials), .env files, source, /etc/passwd; and faf_write could write outside the project. This is a sensitive-information-disclosure (CWE-200) primitive that far exceeds the declared .faf project-context scope. The server runs over stdio, so the read/write is reached by a crafted tool call (e.g. a prompt-injected agent processing attacker-controlled content).
Patches
Fixed in 5.7.2 by confining every caller-supplied path before any filesystem access (safe-path.ts):
- Reads are restricted to .faf / .fafm context files, so non-context files (secrets) are refused regardless of directory.
- General file ops (faf_read / faf_write) are confined to the project root (cwd + system temp; override with FAF_ALLOWED_ROOTS).
- Paths are canonicalized through symlinks (closing the symlink bypass); absolute paths and ../ escapes are rejected; callTool() gains a central PATH-DENIED guard.
Upgrade: npm install -g claude-faf-mcp@5.7.2 (or one-click .mcpb install).
Workarounds
If you cannot upgrade immediately, run the server only against trusted local projects, and set FAF_ALLOWED_ROOTS (patched versions) to a single project directory for a hard directory boundary.
Credits
Identified by the maintainers during a sibling-server audit prompted by the coordinated disclosure of the same class of issue in grok-faf-mcp by Zhihao Zhang (Worcester Polytechnic Institute).
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 5.7.1"
},
"package": {
"ecosystem": "npm",
"name": "claude-faf-mcp"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "5.7.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-200",
"CWE-22",
"CWE-73"
],
"github_reviewed": true,
"github_reviewed_at": "2026-08-19T19:15:25Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "### Summary\n`claude-faf-mcp` MCP tools accept a caller-controlled `path` argument and resolve it (`~` expansion + `path.resolve()`) straight into a filesystem read/write **without confining it to a trusted project directory**. An absolute path or `../` traversal is resolved and used as-is, so the server process can be made to read \u2014 and, via the file tools, write \u2014 files outside the intended `.faf` project context. The only remaining limit is OS file permissions.\n\n### Affected tools\nThe shared `getProjectPath()` chokepoint (feeding the `.faf` tools) and the general-purpose `faf_read` / `faf_write` file tools resolved a caller path straight into a read/write with no confinement (denylist-only); an absolute path still reached home-directory secrets, and `faf_write` could write outside the project.\n\n### Impact\nAn MCP client \u2014 or an LLM prompt-injected via attacker-controlled content (a web page, README, ticket, or `.faf`) into issuing a tool call \u2014 can read any file the server process can read: SSH keys (`~/.ssh/id_rsa`), cloud credentials (`~/.aws/credentials`), `.env` files, source, `/etc/passwd`; and `faf_write` could write outside the project. This is a sensitive-information-disclosure (CWE-200) primitive that far exceeds the declared `.faf` project-context scope. The server runs over stdio, so the read/write is reached by a crafted tool call (e.g. a prompt-injected agent processing attacker-controlled content).\n\n### Patches\nFixed in **5.7.2** by confining every caller-supplied `path` before any filesystem access (`safe-path.ts`):\n- Reads are restricted to `.faf` / `.fafm` context files, so non-context files (secrets) are refused regardless of directory.\n- General file ops (`faf_read` / `faf_write`) are confined to the project root (cwd + system temp; override with `FAF_ALLOWED_ROOTS`).\n- Paths are canonicalized through symlinks (closing the symlink bypass); absolute paths and `../` escapes are rejected; `callTool()` gains a central PATH-DENIED guard.\n\nUpgrade: `npm install -g claude-faf-mcp@5.7.2` (or one-click `.mcpb` install).\n\n### Workarounds\nIf you cannot upgrade immediately, run the server only against trusted local projects, and set `FAF_ALLOWED_ROOTS` (patched versions) to a single project directory for a hard directory boundary.\n\n### Credits\nIdentified by the maintainers during a sibling-server audit prompted by the coordinated disclosure of the same class of issue in `grok-faf-mcp` by **Zhihao Zhang** (Worcester Polytechnic Institute).",
"id": "GHSA-rr55-jp92-8wp2",
"modified": "2026-08-19T19:15:25Z",
"published": "2026-08-19T19:15:25Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/Wolfe-Jam/claude-faf-mcp/security/advisories/GHSA-rr55-jp92-8wp2"
},
{
"type": "PACKAGE",
"url": "https://github.com/Wolfe-Jam/claude-faf-mcp"
},
{
"type": "WEB",
"url": "https://github.com/Wolfe-Jam/claude-faf-mcp/releases/tag/v5.7.2"
}
],
"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"
}
],
"summary": "claude-faf-mcp has an arbitrary local file read/write via unconfined `path` argument in FAF tools"
}
GHSA-RRCW-M6CC-W2CX
Vulnerability from github – Published: 2022-01-05 00:00 – Updated: 2022-09-30 00:00ws-scrcpy is vulnerable to External Control of File Name or Path
{
"affected": [],
"aliases": [
"CVE-2021-3845"
],
"database_specific": {
"cwe_ids": [
"CWE-610",
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2022-01-04T17:15:00Z",
"severity": "HIGH"
},
"details": "ws-scrcpy is vulnerable to External Control of File Name or Path",
"id": "GHSA-rrcw-m6cc-w2cx",
"modified": "2022-09-30T00:00:46Z",
"published": "2022-01-05T00:00:57Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-3845"
},
{
"type": "WEB",
"url": "https://github.com/netristv/ws-scrcpy/commit/e83cf65438bef83a3503b25358bba97bcc156fef"
},
{
"type": "WEB",
"url": "https://huntr.dev/bounties/dc7fc98f-4f4f-440a-b6f6-124a56ea36ef"
}
],
"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"
}
]
}
GHSA-RRWV-G6G5-VJ2P
Vulnerability from github – Published: 2026-02-04 00:30 – Updated: 2026-02-04 00:30i-doit Open Source CMDB 1.14.1 contains a file deletion vulnerability in the import module that allows authenticated attackers to delete arbitrary files by manipulating the delete_import parameter. Attackers can send a POST request to the import module with a crafted filename to remove files from the server's filesystem.
{
"affected": [],
"aliases": [
"CVE-2020-37078"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-02-03T22:16:23Z",
"severity": "HIGH"
},
"details": "i-doit Open Source CMDB 1.14.1 contains a file deletion vulnerability in the import module that allows authenticated attackers to delete arbitrary files by manipulating the delete_import parameter. Attackers can send a POST request to the import module with a crafted filename to remove files from the server\u0027s filesystem.",
"id": "GHSA-rrwv-g6g5-vj2p",
"modified": "2026-02-04T00:30:28Z",
"published": "2026-02-04T00:30:28Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2020-37078"
},
{
"type": "WEB",
"url": "https://sourceforge.net/projects/i-doit"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/48427"
},
{
"type": "WEB",
"url": "https://www.i-doit.org"
},
{
"type": "WEB",
"url": "https://www.vulncheck.com/advisories/i-doit-open-source-cmdb-arbitrary-file-deletion"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/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"
}
]
}
GHSA-RV48-QR4W-FRQJ
Vulnerability from github – Published: 2023-11-15 18:30 – Updated: 2023-11-15 18:30This external control vulnerability, if exploited, could allow a local OS-authenticated user with standard privileges to delete files with System privilege on the machine where these products are installed, resulting in denial of service.
{
"affected": [],
"aliases": [
"CVE-2023-34982"
],
"database_specific": {
"cwe_ids": [
"CWE-610",
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2023-11-15T17:15:41Z",
"severity": "MODERATE"
},
"details": "\nThis external control vulnerability, if exploited, could allow a local OS-authenticated user with standard privileges to delete files with System privilege on the machine where these products are installed, resulting in denial of service.\n\n",
"id": "GHSA-rv48-qr4w-frqj",
"modified": "2023-11-15T18:30:22Z",
"published": "2023-11-15T18:30:22Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-34982"
},
{
"type": "WEB",
"url": "https://www.aveva.com/en/support-and-success/cyber-security-updates"
},
{
"type": "WEB",
"url": "https://www.cisa.gov/news-events/ics-advisories/icsa-23-318-01"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-RW4R-2F9M-M4GF
Vulnerability from github – Published: 2024-05-14 15:32 – Updated: 2024-05-14 15:32NVIDIA Triton Inference Server for Linux contains a vulnerability in the tracing API, where a user can corrupt system files. A successful exploit of this vulnerability might lead to denial of service and data tampering.
{
"affected": [],
"aliases": [
"CVE-2024-0100"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-05-14T14:39:31Z",
"severity": "MODERATE"
},
"details": "NVIDIA Triton Inference Server for Linux contains a vulnerability in the tracing API, where a user can corrupt system files. A successful exploit of this vulnerability might lead to denial of service and data tampering.",
"id": "GHSA-rw4r-2f9m-m4gf",
"modified": "2024-05-14T15:32:51Z",
"published": "2024-05-14T15:32:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-0100"
},
{
"type": "WEB",
"url": "https://nvidia.custhelp.com/app/answers/detail/a_id/5535"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Mitigation
When the set of filenames is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames, 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 provide this capability.
Mitigation
- Run your code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict all access to files within a particular directory.
- Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection.
- This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise.
- Be careful to avoid CWE-243 and other weaknesses related to jails.
Mitigation
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-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
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).
Mitigation
Use OS-level permissions and run as a low-privileged user to limit the scope of any successful attack.
Mitigation
If you are using PHP, configure your application so that it does not use register_globals. During implementation, develop your 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.
Mitigation
Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.
CAPEC-13: Subverting Environment Variable Values
The adversary directly or indirectly modifies environment variables used by or controlling the target software. The adversary's goal is to cause the target software to deviate from its expected operation in a manner that benefits the adversary.
CAPEC-267: Leverage Alternate Encoding
An adversary leverages the possibility to encode potentially harmful input or content used by applications such that the applications are ineffective at validating this encoding standard.
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-72: URL Encoding
This attack targets the encoding of the URL. An adversary can take advantage of the multiple way of encoding an URL and abuse the interpretation of the URL.
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.
CAPEC-80: Using UTF-8 Encoding to Bypass Validation Logic
This attack is a specific variation on leveraging alternate encodings to bypass validation logic. This attack leverages the possibility to encode potentially harmful input in UTF-8 and submit it to applications not expecting or effective at validating this encoding standard making input filtering difficult. UTF-8 (8-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode. Legal UTF-8 characters are one to four bytes long. However, early version of the UTF-8 specification got some entries wrong (in some cases it permitted overlong characters). UTF-8 encoders are supposed to use the "shortest possible" encoding, but naive decoders may accept encodings that are longer than necessary. According to the RFC 3629, a particularly subtle form of this attack can be carried out against a parser which performs security-critical validity checks against the UTF-8 encoded form of its input, but interprets certain illegal octet sequences as characters.