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.
13197 vulnerabilities reference this CWE, most recent first.
GHSA-87R4-WG36-7X2V
Vulnerability from github – Published: 2025-01-04 15:30 – Updated: 2025-01-04 15:30IBM Engineering Lifecycle Optimization - Publishing 7.0.2 and 7.0.3 could allow a remote attacker to traverse directories on the system. An attacker could send a specially crafted URL request containing "dot dot" sequences (/../) to view arbitrary files on the system.
{
"affected": [],
"aliases": [
"CVE-2024-41765"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-01-04T15:15:06Z",
"severity": "MODERATE"
},
"details": "IBM Engineering Lifecycle Optimization - Publishing 7.0.2 and 7.0.3 could allow a remote attacker to traverse directories on the system. An attacker could send a specially crafted URL request containing \"dot dot\" sequences (/../) to view arbitrary files on the system.",
"id": "GHSA-87r4-wg36-7x2v",
"modified": "2025-01-04T15:30:45Z",
"published": "2025-01-04T15:30:45Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-41765"
},
{
"type": "WEB",
"url": "https://www.ibm.com/support/pages/node/7180201"
}
],
"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-87V5-P656-XR8X
Vulnerability from github – Published: 2022-12-25 06:30 – Updated: 2025-04-15 15:30An issue was discovered in Simmeth Lieferantenmanager before 5.6. An attacker can download arbitrary files from the web server by abusing an API call: /DS/LM_API/api/ConfigurationService/GetImages with an '"ImagesPath":"C:\"' value.
{
"affected": [],
"aliases": [
"CVE-2022-44016"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2022-12-25T05:15:00Z",
"severity": "HIGH"
},
"details": "An issue was discovered in Simmeth Lieferantenmanager before 5.6. An attacker can download arbitrary files from the web server by abusing an API call: /DS/LM_API/api/ConfigurationService/GetImages with an \u0027\"ImagesPath\":\"C:\\\\\"\u0027 value.",
"id": "GHSA-87v5-p656-xr8x",
"modified": "2025-04-15T15:30:46Z",
"published": "2022-12-25T06:30:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-44016"
},
{
"type": "WEB",
"url": "https://sec-consult.com/vulnerability-lab/advisory/multiple-critical-vulnerabilities-in-simmeth-system-gmbh-lieferantenmanager"
}
],
"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-87VG-5PGX-PGGH
Vulnerability from github – Published: 2022-05-13 01:07 – Updated: 2024-04-12 21:24Addresses partial fix in CVE-2018-1261. Pivotal spring-integration-zip, versions prior to 1.0.2, exposes an arbitrary file write vulnerability, that can be achieved using a specially crafted zip archive (affects other archives as well, bzip2, tar, xz, war, cpio, 7z), that holds path traversal filenames. So when the filename gets concatenated to the target extraction directory, the final path ends up outside of the target folder.
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "org.springframework.integration:spring-integration-zip"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.0.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2018-1263"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": true,
"github_reviewed_at": "2023-07-19T23:55:10Z",
"nvd_published_at": "2018-05-15T20:29:00Z",
"severity": "MODERATE"
},
"details": "Addresses partial fix in CVE-2018-1261. Pivotal spring-integration-zip, versions prior to 1.0.2, exposes an arbitrary file write vulnerability, that can be achieved using a specially crafted zip archive (affects other archives as well, bzip2, tar, xz, war, cpio, 7z), that holds path traversal filenames. So when the filename gets concatenated to the target extraction directory, the final path ends up outside of the target folder.",
"id": "GHSA-87vg-5pgx-pggh",
"modified": "2024-04-12T21:24:22Z",
"published": "2022-05-13T01:07:04Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2018-1263"
},
{
"type": "WEB",
"url": "https://github.com/spring-projects/spring-integration-extensions/commit/d10f537283d90eabd28af57ac97f860a3913bf9b"
},
{
"type": "PACKAGE",
"url": "https://github.com/spring-projects/spring-integration"
},
{
"type": "WEB",
"url": "https://pivotal.io/security/cve-2018-1263"
},
{
"type": "WEB",
"url": "https://web.archive.org/web/20210125210559/https://www.securityfocus.com/bid/104179"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N",
"type": "CVSS_V3"
}
],
"summary": "spring-integration-zip Arbitrary File Write"
}
GHSA-87X6-4Q8J-CG2M
Vulnerability from github – Published: 2025-04-17 18:31 – Updated: 2026-04-01 18:34Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') vulnerability in WP Asia MyTicket Events allows Path Traversal. This issue affects MyTicket Events: from n/a through 1.2.4.
{
"affected": [],
"aliases": [
"CVE-2025-27299"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-04-17T16:15:36Z",
"severity": "MODERATE"
},
"details": "Improper Limitation of a Pathname to a Restricted Directory (\u0027Path Traversal\u0027) vulnerability in WP Asia MyTicket Events allows Path Traversal. This issue affects MyTicket Events: from n/a through 1.2.4.",
"id": "GHSA-87x6-4q8j-cg2m",
"modified": "2026-04-01T18:34:47Z",
"published": "2025-04-17T18:31:14Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-27299"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/wordpress/plugin/myticket-events/vulnerability/wordpress-myticket-events-plugin-1-2-4-non-arbitrary-file-read-vulnerability?_s_id=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-87XH-F8RH-5HGQ
Vulnerability from github – Published: 2022-05-24 19:19 – Updated: 2022-05-24 19:19In Mahara before 20.04.5, 20.10.3, 21.04.2, and 21.10.0, adjusting the path component for the page help file allows attackers to bypass the intended access control for HTML files via directory traversal. It replaces the - character with the / character.
{
"affected": [],
"aliases": [
"CVE-2021-43264"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2021-11-02T22:15:00Z",
"severity": "LOW"
},
"details": "In Mahara before 20.04.5, 20.10.3, 21.04.2, and 21.10.0, adjusting the path component for the page help file allows attackers to bypass the intended access control for HTML files via directory traversal. It replaces the - character with the / character.",
"id": "GHSA-87xh-f8rh-5hgq",
"modified": "2022-05-24T19:19:40Z",
"published": "2022-05-24T19:19:40Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-43264"
},
{
"type": "WEB",
"url": "https://bugs.launchpad.net/mahara/+bug/1944979"
},
{
"type": "WEB",
"url": "https://mahara.org/interaction/forum/topic.php?id=8954"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-8832-5JJ9-833X
Vulnerability from github – Published: 2024-09-10 15:31 – Updated: 2024-09-10 15:31A improper limitation of a pathname to a restricted directory ('path traversal') in Fortinet FortiClientEMS versions 7.2.0 through 7.2.4, 7.0.0 through 7.0.13, 6.4.0 through 6.4.9, 6.2.0 through 6.2.9, 6.0.0 through 6.0.8, 1.2.1 through 1.2.5 allows attacker to perform a denial of service, read or write a limited number of files via specially crafted HTTP requests
{
"affected": [],
"aliases": [
"CVE-2024-21753"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-09-10T15:15:14Z",
"severity": "MODERATE"
},
"details": "A improper limitation of a pathname to a restricted directory (\u0027path traversal\u0027) in Fortinet FortiClientEMS versions 7.2.0 through 7.2.4, 7.0.0 through 7.0.13, 6.4.0 through 6.4.9, 6.2.0 through 6.2.9, 6.0.0 through 6.0.8, 1.2.1 through 1.2.5 allows attacker to perform a denial of service, read or write a limited number of files via specially crafted HTTP requests",
"id": "GHSA-8832-5jj9-833x",
"modified": "2024-09-10T15:31:04Z",
"published": "2024-09-10T15:31:04Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-21753"
},
{
"type": "WEB",
"url": "https://fortiguard.fortinet.com/psirt/FG-IR-23-362"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-8835-PQF9-C9CQ
Vulnerability from github – Published: 2023-11-23 15:30 – Updated: 2023-11-23 15:30Path traversal vulnerability whose exploitation could allow an authenticated remote user to bypass SecurityManager's intended restrictions and list a parent directory via any filename, such as a multiple ..%2F value affecting the 'dodoc' parameter in the /MailAdmin_dll.htm file.
{
"affected": [],
"aliases": [
"CVE-2023-4593"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2023-11-23T13:15:11Z",
"severity": "MODERATE"
},
"details": "Path traversal vulnerability whose exploitation could allow an authenticated remote user to bypass SecurityManager\u0027s intended restrictions and list a parent directory via any filename, such as a multiple ..%2F value affecting the \u0027dodoc\u0027 parameter in the /MailAdmin_dll.htm file.",
"id": "GHSA-8835-pqf9-c9cq",
"modified": "2023-11-23T15:30:25Z",
"published": "2023-11-23T15:30:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-4593"
},
{
"type": "WEB",
"url": "https://www.incibe.es/en/incibe-cert/notices/aviso/multiple-vulnerabilities-bvrp-software-slmail"
}
],
"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-883Q-V52W-XP4C
Vulnerability from github – Published: 2022-05-17 00:41 – Updated: 2022-05-17 00:41Directory traversal vulnerability in captcha/captcha_image.php in the RWCards (com_rwcards) 3.0.11 component for Joomla!, when magic_quotes_gpc is disabled, allows remote attackers to include and execute arbitrary local files via directory traversal sequences in the img parameter.
{
"affected": [],
"aliases": [
"CVE-2008-6172"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2009-02-19T16:30:00Z",
"severity": "MODERATE"
},
"details": "Directory traversal vulnerability in captcha/captcha_image.php in the RWCards (com_rwcards) 3.0.11 component for Joomla!, when magic_quotes_gpc is disabled, allows remote attackers to include and execute arbitrary local files via directory traversal sequences in the img parameter.",
"id": "GHSA-883q-v52w-xp4c",
"modified": "2022-05-17T00:41:08Z",
"published": "2022-05-17T00:41:08Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2008-6172"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/46081"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/6817"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/32367"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/31892"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-8847-338W-5HCJ
Vulnerability from github – Published: 2026-04-22 17:43 – Updated: 2026-05-13 13:30Summary
Versions of i18next-fs-backend prior to 2.6.4 interpolate the caller-supplied lng and ns values directly into the configured loadPath and addPath templates with no path-component validation and no sanitisation. When an application exposes the resolved language code to user-controlled input (?lng= query parameter, cookie, request header), a crafted value can break out of the intended locale directory.
Affected call sites in lib/index.js:
read(line 38 pre-patch):const filename = interpolate(loadPath, { lng: language, ns: namespace })removeFile(line 101 pre-patch): same pattern againstaddPathwriteFile(line 127 pre-patch): same pattern againstaddPathfor queued missing-key writes
The helper interpolate in lib/utils.js substitutes raw values with no encoding — unlike the addQueryString helper in i18next-http-backend, there is no equivalent safety for path interpolation.
Impact
- Arbitrary file read. With a
loadPathlike/locales/{{lng}}/{{ns}}.json, an attacker-controlledlng = '../../etc'(and matchingns) causes the backend to read a file outside the locale directory. For parsers that tolerate arbitrary content (YAML's freeform text), the file contents surface as a translation resource. - Arbitrary file overwrite.
addPathis interpolated the same way for missing-key writes (thecreate()code path and the debounced writer inwriteFile). A traversinglng/nscombination can cause the process to write JSON structures to an unintended filesystem location, potentially overwriting application files if the process user has write access. - Chain with
.js/.tseval.i18next-fs-backendsupports loading.jsand.tslocale files byeval-ing their content (intentional feature, documented as requiring trusted sources). Combining traversal with that path — for examplelng = '../../../app/config'againstloadPath: '/locales/{{lng}}/{{ns}}.js'— would cause the backend to execute a server-side file as JavaScript, exfiltrating whatever it can touch (process.env, connected services).
Exploitation requires the application to pass an untrusted lng/ns value through to i18next.t() without its own validation. Many i18next setups do exactly this via i18next-browser-languagedetector (query string / cookie detection).
Affected versions
All versions of i18next-fs-backend prior to 2.6.4.
Patch
Fixed in 2.6.4. lib/utils.js now exports:
isSafePathSegment(v)— returnstrueonly ifvis a non-empty string of ≤ 128 chars that does not contain..,/,\, control characters, or a prototype key (__proto__,constructor,prototype). Legitimate i18next language-code shapes (BCP-47,en_US,zh-Hant-HK,pirate-speak,my-custom.ns,+-joined multi-language values) all pass.interpolatePath(template, data)— substitutes variables like the existinginterpolatebut refuses the whole result if any segment failsisSafePathSegment. Callers bail out with an error (read) or silently drop the queued write (writeFile,removeFile).
The .js / .ts eval behaviour is intentionally retained — dynamic expressions in locale files are a documented feature of this backend, and safe replacements like dynamic import() are async-only and incompatible with this backend's sync-capable code path. The README has a new "Security considerations" section that spells out the trust model: .js/.ts locale files must be treated as code.
Workarounds
No workaround short of upgrading. If you cannot upgrade immediately, sanitise lng / ns at your application boundary before passing them to i18next — reject values containing .., /, \, control characters, and cap the length.
Credits
Discovered via an internal security audit of the i18next ecosystem.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "i18next-fs-backend"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.6.4"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-41693"
],
"database_specific": {
"cwe_ids": [
"CWE-22",
"CWE-73"
],
"github_reviewed": true,
"github_reviewed_at": "2026-04-22T17:43:14Z",
"nvd_published_at": "2026-05-08T16:16:11Z",
"severity": "HIGH"
},
"details": "### Summary\n\nVersions of `i18next-fs-backend` prior to 2.6.4 interpolate the caller-supplied `lng` and `ns` values directly into the configured `loadPath` and `addPath` templates with no path-component validation and no sanitisation. When an application exposes the resolved language code to user-controlled input (`?lng=` query parameter, cookie, request header), a crafted value can break out of the intended locale directory.\n\nAffected call sites in `lib/index.js`:\n\n- `read` (line 38 pre-patch): `const filename = interpolate(loadPath, { lng: language, ns: namespace })`\n- `removeFile` (line 101 pre-patch): same pattern against `addPath`\n- `writeFile` (line 127 pre-patch): same pattern against `addPath` for queued missing-key writes\n\nThe helper `interpolate` in `lib/utils.js` substitutes raw values with no encoding \u2014 unlike the `addQueryString` helper in `i18next-http-backend`, there is no equivalent safety for path interpolation.\n\n### Impact\n\n- **Arbitrary file read.** With a `loadPath` like `/locales/{{lng}}/{{ns}}.json`, an attacker-controlled `lng = \u0027../../etc\u0027` (and matching `ns`) causes the backend to read a file outside the locale directory. For parsers that tolerate arbitrary content (YAML\u0027s freeform text), the file contents surface as a translation resource.\n- **Arbitrary file overwrite.** `addPath` is interpolated the same way for missing-key writes (the `create()` code path and the debounced writer in `writeFile`). A traversing `lng`/`ns` combination can cause the process to write JSON structures to an unintended filesystem location, potentially overwriting application files if the process user has write access.\n- **Chain with `.js`/`.ts` eval.** `i18next-fs-backend` supports loading `.js` and `.ts` locale files by `eval`-ing their content (intentional feature, documented as requiring trusted sources). Combining traversal with that path \u2014 for example `lng = \u0027../../../app/config\u0027` against `loadPath: \u0027/locales/{{lng}}/{{ns}}.js\u0027` \u2014 would cause the backend to **execute** a server-side file as JavaScript, exfiltrating whatever it can touch (`process.env`, connected services).\n\nExploitation requires the application to pass an untrusted `lng`/`ns` value through to `i18next.t()` without its own validation. Many i18next setups do exactly this via `i18next-browser-languagedetector` (query string / cookie detection).\n\n### Affected versions\n\nAll versions of `i18next-fs-backend` prior to **2.6.4**.\n\n### Patch\n\nFixed in **2.6.4**. `lib/utils.js` now exports:\n\n- `isSafePathSegment(v)` \u2014 returns `true` only if `v` is a non-empty string of \u2264 128 chars that does not contain `..`, `/`, `\\`, control characters, or a prototype key (`__proto__`, `constructor`, `prototype`). Legitimate i18next language-code shapes (BCP-47, `en_US`, `zh-Hant-HK`, `pirate-speak`, `my-custom.ns`, `+`-joined multi-language values) all pass.\n- `interpolatePath(template, data)` \u2014 substitutes variables like the existing `interpolate` but refuses the whole result if any segment fails `isSafePathSegment`. Callers bail out with an error (`read`) or silently drop the queued write (`writeFile`, `removeFile`).\n\nThe `.js` / `.ts` `eval` behaviour is intentionally retained \u2014 dynamic expressions in locale files are a documented feature of this backend, and safe replacements like dynamic `import()` are async-only and incompatible with this backend\u0027s sync-capable code path. The README has a new \"Security considerations\" section that spells out the trust model: `.js`/`.ts` locale files must be treated as code.\n\n### Workarounds\n\nNo workaround short of upgrading. If you cannot upgrade immediately, sanitise `lng` / `ns` at your application boundary before passing them to i18next \u2014 reject values containing `..`, `/`, `\\`, control characters, and cap the length.\n\n### Credits\n\nDiscovered via an internal security audit of the i18next ecosystem.",
"id": "GHSA-8847-338w-5hcj",
"modified": "2026-05-13T13:30:00Z",
"published": "2026-04-22T17:43:14Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/i18next/i18next-fs-backend/security/advisories/GHSA-8847-338w-5hcj"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41693"
},
{
"type": "PACKAGE",
"url": "https://github.com/i18next/i18next-fs-backend"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "i18next-fs-backend: Path traversal via unsanitised lng/ns allows arbitrary file read/overwrite"
}
GHSA-884H-QC27-GHCQ
Vulnerability from github – Published: 2022-05-01 23:37 – Updated: 2022-05-01 23:37Absolute path traversal vulnerability in the FTP server in MicroWorld eScan Corporate Edition 9.0.742.98 and eScan Management Console (aka eScan Server) 9.0.742.1 allows remote attackers to read arbitrary files via an absolute pathname in the RETR (get) command.
{
"affected": [],
"aliases": [
"CVE-2008-1221"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2008-03-10T17:44:00Z",
"severity": "MODERATE"
},
"details": "Absolute path traversal vulnerability in the FTP server in MicroWorld eScan Corporate Edition 9.0.742.98 and eScan Management Console (aka eScan Server) 9.0.742.1 allows remote attackers to read arbitrary files via an absolute pathname in the RETR (get) command.",
"id": "GHSA-884h-qc27-ghcq",
"modified": "2022-05-01T23:37:48Z",
"published": "2022-05-01T23:37:48Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2008-1221"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/41033"
},
{
"type": "WEB",
"url": "http://aluigi.altervista.org/adv/escaz-adv.txt"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/29246"
},
{
"type": "WEB",
"url": "http://securityreason.com/securityalert/3723"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/archive/1/489228/100/0/threaded"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/28127"
}
],
"schema_version": "1.4.0",
"severity": []
}
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.