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.
13297 vulnerabilities reference this CWE, most recent first.
GHSA-M733-5W8F-5GGW
Vulnerability from github – Published: 2026-01-26 21:02 – Updated: 2026-01-29 03:23Summary
When pnpm installs a file: (directory) or git: dependency, it follows symlinks and reads their target contents without constraining them to the package root. A malicious package containing a symlink to an absolute path (e.g., /etc/passwd, ~/.ssh/id_rsa) causes pnpm to copy that file's contents into node_modules, leaking local data.
Preconditions: Only affects file: and git: dependencies. Registry packages (npm) have symlinks stripped during publish and are NOT affected.
Details
The vulnerability exists in store/cafs/src/addFilesFromDir.ts. The code uses fs.statSync() and readFileSync() which follow symlinks by default:
const absolutePath = path.join(dirname, relativePath)
const stat = fs.statSync(absolutePath) // Follows symlinks!
const buffer = fs.readFileSync(absolutePath) // Reads symlink TARGET
There is no check that absolutePath resolves to a location inside the package directory.
PoC
# Create malicious package
mkdir -p /tmp/evil && cd /tmp/evil
ln -s /etc/passwd leaked-passwd.txt
echo '{"name":"evil","version":"1.0.0","files":["*.txt"]}' > package.json
# Victim installs
mkdir /tmp/victim && cd /tmp/victim
pnpm init && pnpm add file:../evil
# Leaked!
cat node_modules/evil/leaked-passwd.txt
Impact
- Developers installing local/file dependencies
- CI/CD pipelines installing git dependencies
- Credential theft via symlinks to
~/.aws/credentials,~/.npmrc,~/.ssh/id_rsa
Suggested Fix
Use lstatSync to detect symlinks and reject those pointing outside the package root in store/cafs/src/addFilesFromDir.ts.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "pnpm"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "10.28.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-24056"
],
"database_specific": {
"cwe_ids": [
"CWE-22",
"CWE-59"
],
"github_reviewed": true,
"github_reviewed_at": "2026-01-26T21:02:33Z",
"nvd_published_at": "2026-01-26T22:15:56Z",
"severity": "MODERATE"
},
"details": "### Summary\nWhen pnpm installs a `file:` (directory) or `git:` dependency, it follows symlinks and reads their target contents without constraining them to the package root. A malicious package containing a symlink to an absolute path (e.g., `/etc/passwd`, `~/.ssh/id_rsa`) causes pnpm to copy that file\u0027s contents into `node_modules`, leaking local data.\n\n**Preconditions:** Only affects `file:` and `git:` dependencies. Registry packages (npm) have symlinks stripped during publish and are NOT affected.\n\n### Details\nThe vulnerability exists in `store/cafs/src/addFilesFromDir.ts`. The code uses `fs.statSync()` and `readFileSync()` which follow symlinks by default:\n\n```typescript\nconst absolutePath = path.join(dirname, relativePath)\nconst stat = fs.statSync(absolutePath) // Follows symlinks!\nconst buffer = fs.readFileSync(absolutePath) // Reads symlink TARGET\n```\n\nThere is no check that `absolutePath` resolves to a location inside the package directory.\n\n### PoC\n```bash\n# Create malicious package\nmkdir -p /tmp/evil \u0026\u0026 cd /tmp/evil\nln -s /etc/passwd leaked-passwd.txt\necho \u0027{\"name\":\"evil\",\"version\":\"1.0.0\",\"files\":[\"*.txt\"]}\u0027 \u003e package.json\n\n# Victim installs\nmkdir /tmp/victim \u0026\u0026 cd /tmp/victim\npnpm init \u0026\u0026 pnpm add file:../evil\n\n# Leaked!\ncat node_modules/evil/leaked-passwd.txt\n```\n\n### Impact\n- Developers installing local/file dependencies\n- CI/CD pipelines installing git dependencies\n- Credential theft via symlinks to `~/.aws/credentials`, `~/.npmrc`, `~/.ssh/id_rsa`\n\n### Suggested Fix\nUse `lstatSync` to detect symlinks and reject those pointing outside the package root in `store/cafs/src/addFilesFromDir.ts`.",
"id": "GHSA-m733-5w8f-5ggw",
"modified": "2026-01-29T03:23:22Z",
"published": "2026-01-26T21:02:33Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/pnpm/pnpm/security/advisories/GHSA-m733-5w8f-5ggw"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-24056"
},
{
"type": "WEB",
"url": "https://github.com/pnpm/pnpm/commit/b277b45bc35ae77ca72d7634d144bbd58a48b70f"
},
{
"type": "PACKAGE",
"url": "https://github.com/pnpm/pnpm"
},
{
"type": "WEB",
"url": "https://github.com/pnpm/pnpm/releases/tag/v10.28.2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "pnpm has symlink traversal in file:/git dependencies"
}
GHSA-M735-JRV9-J3FC
Vulnerability from github – Published: 2026-06-20 03:32 – Updated: 2026-06-20 03:32The Database for Contact Form 7, WPforms, Elementor forms plugin for WordPress is vulnerable to arbitrary file deletion due to insufficient file path validation in the view_page function in all versions up to, and including, 1.5.1. This makes it possible for unauthenticated attackers to delete arbitrary files on the server, which can easily lead to remote code execution when the right file is deleted (such as wp-config.php). Successful exploitation requires an administrator to view or edit the poisoned form entry, at which point PHP's bracket parser reshapes the attacker-crafted JSON key to bypass the stored-path isset check and trigger deletion of the traversal-specified file.
{
"affected": [],
"aliases": [
"CVE-2026-9843"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-20T02:16:26Z",
"severity": "HIGH"
},
"details": "The Database for Contact Form 7, WPforms, Elementor forms plugin for WordPress is vulnerable to arbitrary file deletion due to insufficient file path validation in the view_page function in all versions up to, and including, 1.5.1. This makes it possible for unauthenticated attackers to delete arbitrary files on the server, which can easily lead to remote code execution when the right file is deleted (such as wp-config.php). Successful exploitation requires an administrator to view or edit the poisoned form entry, at which point PHP\u0027s bracket parser reshapes the attacker-crafted JSON key to bypass the stored-path isset check and trigger deletion of the traversal-specified file.",
"id": "GHSA-m735-jrv9-j3fc",
"modified": "2026-06-20T03:32:30Z",
"published": "2026-06-20T03:32:30Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9843"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/contact-form-entries/tags/1.5.1/contact-form-entries.php#L435"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/contact-form-entries/tags/1.5.1/contact-form-entries.php#L747"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/contact-form-entries/tags/1.5.1/includes/data.php#L539"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/contact-form-entries/tags/1.5.1/includes/plugin-pages.php#L1197"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/contact-form-entries/tags/1.5.1/templates/view.php#L559"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/changeset/3578556/contact-form-entries"
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/4169b390-0972-4aa9-ae04-f5f67afe15ef?source=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-M738-M34Q-2XGP
Vulnerability from github – Published: 2026-05-12 15:31 – Updated: 2026-05-12 15:31CWE-22: Improper Limitation of a Pathname to a Restricted Directory (“Path Traversal”) vulnerability that could cause unauthorized access to sensitive files when user-supplied input is improperly handled during server-side file path processing.
{
"affected": [],
"aliases": [
"CVE-2026-6865"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-12T14:17:10Z",
"severity": "HIGH"
},
"details": "CWE-22: Improper Limitation of a Pathname to a Restricted Directory (\u201cPath Traversal\u201d) vulnerability that could cause unauthorized access to sensitive files when user-supplied input is improperly handled during server-side file path processing.",
"id": "GHSA-m738-m34q-2xgp",
"modified": "2026-05-12T15:31:41Z",
"published": "2026-05-12T15:31:41Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-6865"
},
{
"type": "WEB",
"url": "https://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2026-132-03\u0026p_enDocType=Security+and+Safety+Notice\u0026p_File_Name=SEVD-2026-132-03.pdf"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/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"
}
]
}
GHSA-M73P-W5W2-3M5H
Vulnerability from github – Published: 2025-02-28 00:30 – Updated: 2025-02-28 18:31In XIQ-SE before 24.2.11, due to a missing access control check, a path traversal is possible, which may lead to privilege escalation.
{
"affected": [],
"aliases": [
"CVE-2024-38292"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-02-27T22:15:38Z",
"severity": "CRITICAL"
},
"details": "In XIQ-SE before 24.2.11, due to a missing access control check, a path traversal is possible, which may lead to privilege escalation.",
"id": "GHSA-m73p-w5w2-3m5h",
"modified": "2025-02-28T18:31:02Z",
"published": "2025-02-28T00:30:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-38292"
},
{
"type": "WEB",
"url": "https://community.extremenetworks.com/t5/security-advisories-formerly/sa-2024-104-xiq-se-path-traversal-privilege-escalation-cve-2024/ba-p/116362"
}
],
"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:H",
"type": "CVSS_V3"
}
]
}
GHSA-M754-Q244-3CRW
Vulnerability from github – Published: 2022-01-14 00:02 – Updated: 2022-01-20 00:02This affects the package Crow before 0.3+4. It is possible to traverse directories to fetch arbitrary files from the server.
{
"affected": [],
"aliases": [
"CVE-2021-23514"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2022-01-13T14:15:00Z",
"severity": "HIGH"
},
"details": "This affects the package Crow before 0.3+4. It is possible to traverse directories to fetch arbitrary files from the server.",
"id": "GHSA-m754-q244-3crw",
"modified": "2022-01-20T00:02:15Z",
"published": "2022-01-14T00:02:19Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-23514"
},
{
"type": "WEB",
"url": "https://github.com/CrowCpp/Crow/pull/317"
},
{
"type": "WEB",
"url": "https://github.com/CrowCpp/Crow/releases/tag/v0.3%2B4"
},
{
"type": "WEB",
"url": "https://snyk.io/vuln/SNYK-UNMANAGED-CROW-2336163"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-M78R-R2PF-69WJ
Vulnerability from github – Published: 2026-01-17 03:30 – Updated: 2026-01-17 03:30The Feeds for YouTube Pro plugin for WordPress is vulnerable to arbitrary file read in all versions up to, and including, 2.6.0 via the 'sby_check_wp_submit' AJAX action. This is due to insufficient sanitization of user-supplied data and the use of that data in a file operation. This makes it possible for unauthenticated attackers to read the contents of arbitrary files on the server, which can contain sensitive information, granted the 'Save Featured Images' setting is enabled and 'Disable WP Posts' is disabled. Note: This vulnerability only affects the Pro version of Feeds for YouTube.
{
"affected": [],
"aliases": [
"CVE-2025-12002"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-01-17T03:16:02Z",
"severity": "MODERATE"
},
"details": "The Feeds for YouTube Pro plugin for WordPress is vulnerable to arbitrary file read in all versions up to, and including, 2.6.0 via the \u0027sby_check_wp_submit\u0027 AJAX action. This is due to insufficient sanitization of user-supplied data and the use of that data in a file operation. This makes it possible for unauthenticated attackers to read the contents of arbitrary files on the server, which can contain sensitive information, granted the \u0027Save Featured Images\u0027 setting is enabled and \u0027Disable WP Posts\u0027 is disabled. Note: This vulnerability only affects the Pro version of Feeds for YouTube.",
"id": "GHSA-m78r-r2pf-69wj",
"modified": "2026-01-17T03:30:24Z",
"published": "2026-01-17T03:30:24Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-12002"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/feeds-for-youtube/trunk/inc/Services/AdminAjaxService.php#L25"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/feeds-for-youtube/trunk/inc/Services/AdminAjaxService.php#L339"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/feeds-for-youtube/trunk/inc/Services/AdminAjaxService.php#L383"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/feeds-for-youtube/trunk/inc/sby-functions.php#L1038"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/feeds-for-youtube/trunk/inc/sby-functions.php#L1047"
},
{
"type": "WEB",
"url": "https://smashballoon.com/youtube-feed"
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/e9f31ec5-c376-45b1-9ffe-35c80b89b60d?source=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-M792-XQC7-323V
Vulnerability from github – Published: 2022-05-13 01:10 – Updated: 2022-05-13 01:10A path traversal vulnerability in the web application component of Micro Focus Filr 3.x allows a remote attacker authenticated as a low privilege user to download arbitrary files from the Filr server. This vulnerability affects all versions of Filr 3.x prior to Security Update 6.
{
"affected": [],
"aliases": [
"CVE-2019-3474"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2019-02-20T22:29:00Z",
"severity": "MODERATE"
},
"details": "A path traversal vulnerability in the web application component of Micro Focus Filr 3.x allows a remote attacker authenticated as a low privilege user to download arbitrary files from the Filr server. This vulnerability affects all versions of Filr 3.x prior to Security Update 6.",
"id": "GHSA-m792-xqc7-323v",
"modified": "2022-05-13T01:10:19Z",
"published": "2022-05-13T01:10:19Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-3474"
},
{
"type": "WEB",
"url": "https://download.novell.com/Download?buildid=nZUCSDkvpxk~"
},
{
"type": "WEB",
"url": "https://support.microfocus.com/kb/doc.php?id=7023726"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/46450"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-M79G-CRVQ-57HP
Vulnerability from github – Published: 2025-08-09 15:30 – Updated: 2025-08-09 15:30A vulnerability, which was classified as critical, has been found in linlinjava litemall up to 1.8.0. Affected by this issue is the function delete of the file /admin/storage/delete of the component File Handler. The manipulation of the argument key leads to path traversal. The attack may be launched remotely. The exploit has been disclosed to the public and may be used.
{
"affected": [],
"aliases": [
"CVE-2025-8753"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-08-09T14:15:26Z",
"severity": "MODERATE"
},
"details": "A vulnerability, which was classified as critical, has been found in linlinjava litemall up to 1.8.0. Affected by this issue is the function delete of the file /admin/storage/delete of the component File Handler. The manipulation of the argument key leads to path traversal. The attack may be launched remotely. The exploit has been disclosed to the public and may be used.",
"id": "GHSA-m79g-crvq-57hp",
"modified": "2025-08-09T15:30:21Z",
"published": "2025-08-09T15:30:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-8753"
},
{
"type": "WEB",
"url": "https://github.com/linlinjava/litemall/issues/564"
},
{
"type": "WEB",
"url": "https://github.com/linlinjava/litemall/issues/564#issue-3267670352"
},
{
"type": "WEB",
"url": "https://vuldb.com/?ctiid.319250"
},
{
"type": "WEB",
"url": "https://vuldb.com/?id.319250"
},
{
"type": "WEB",
"url": "https://vuldb.com/?submit.623859"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/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-M7CF-9JQX-8XRQ
Vulnerability from github – Published: 2022-05-13 01:44 – Updated: 2022-05-13 01:44Leptonica 1.74.4 constructs unintended pathnames (containing duplicated path components) when operating on files in /tmp subdirectories, which might allow local users to bypass intended file restrictions by leveraging access to a directory located deeper within the /tmp directory tree, as demonstrated by /tmp/ANY/PATH/ANY/PATH/input.tif.
{
"affected": [],
"aliases": [
"CVE-2017-18196"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2018-02-23T21:29:00Z",
"severity": "LOW"
},
"details": "Leptonica 1.74.4 constructs unintended pathnames (containing duplicated path components) when operating on files in /tmp subdirectories, which might allow local users to bypass intended file restrictions by leveraging access to a directory located deeper within the /tmp directory tree, as demonstrated by /tmp/ANY/PATH/ANY/PATH/input.tif.",
"id": "GHSA-m7cf-9jqx-8xrq",
"modified": "2022-05-13T01:44:36Z",
"published": "2022-05-13T01:44:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2017-18196"
},
{
"type": "WEB",
"url": "https://bugs.debian.org/885704"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-M7F6-RHXQ-9PJX
Vulnerability from github – Published: 2022-05-01 23:30 – Updated: 2022-05-01 23:30Directory traversal vulnerability in update/index.php in Liquid-Silver CMS 0.35, when magic_quotes_gpc is disabled, allows remote attackers to include and execute arbitrary local files via a .. (dot dot) in the update parameter.
{
"affected": [],
"aliases": [
"CVE-2008-0459"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2008-01-25T16:00:00Z",
"severity": "MODERATE"
},
"details": "Directory traversal vulnerability in update/index.php in Liquid-Silver CMS 0.35, when magic_quotes_gpc is disabled, allows remote attackers to include and execute arbitrary local files via a .. (dot dot) in the update parameter.",
"id": "GHSA-m7f6-rhxq-9pjx",
"modified": "2022-05-01T23:30:31Z",
"published": "2022-05-01T23:30:31Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2008-0459"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/39895"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/4976"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/28619"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/27425"
},
{
"type": "WEB",
"url": "http://www.vupen.com/english/advisories/2008/0309"
}
],
"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.