CVE-2026-4867 - High Severity Vulnerability
Vulnerable Library - path-to-regexp-0.1.12.tgz
Express style path to RegExp utility
Library home page: https://registry.npmjs.org/path-to-regexp/-/path-to-regexp-0.1.12.tgz
Path to dependency file: /package.json
Path to vulnerable library: /package.json
Dependency Hierarchy:
- express-4.21.2.tgz (Root Library)
- ❌ path-to-regexp-0.1.12.tgz (Vulnerable Library)
Found in base branch: csl
Vulnerability Details
Impact:
A bad regular expression is generated any time you have three or more parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b-:c or /:a-:b-:c-:d. The backtrack protection added in path-to-regexp@0.1.12 only prevents ambiguity for two parameters. With three or more, the generated lookahead does not block single separator characters, so capture groups overlap and cause catastrophic backtracking.
Patches:
Upgrade to path-to-regexp@0.1.13
Custom regex patterns in route definitions (e.g., /:a-:b([^-/]+)-:c([^-/]+)) are not affected because they override the default capture group.
Workarounds:
All versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b-:c to /:a-:b([^-/]+)-:c([^-/]+).
If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length.
Publish Date: 2026-03-26
URL: CVE-2026-4867
CVSS 3 Score Details (7.5)
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: None
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: None
- Integrity Impact: None
- Availability Impact: High
For more information on CVSS3 Scores, click here.
Suggested Fix
Type: Upgrade version
Origin: GHSA-37ch-88jc-xwx2
Release Date: 2026-03-26
Fix Resolution: path-to-regexp - 0.1.13
CVE-2026-4867 - High Severity Vulnerability
Express style path to RegExp utility
Library home page: https://registry.npmjs.org/path-to-regexp/-/path-to-regexp-0.1.12.tgz
Path to dependency file: /package.json
Path to vulnerable library: /package.json
Dependency Hierarchy:
Found in base branch: csl
Impact:
A bad regular expression is generated any time you have three or more parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b-:c or /:a-:b-:c-:d. The backtrack protection added in path-to-regexp@0.1.12 only prevents ambiguity for two parameters. With three or more, the generated lookahead does not block single separator characters, so capture groups overlap and cause catastrophic backtracking.
Patches:
Upgrade to path-to-regexp@0.1.13
Custom regex patterns in route definitions (e.g., /:a-:b([^-/]+)-:c([^-/]+)) are not affected because they override the default capture group.
Workarounds:
All versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b-:c to /:a-:b([^-/]+)-:c([^-/]+).
If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length.
Publish Date: 2026-03-26
URL: CVE-2026-4867
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: None
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: None
- Integrity Impact: None
- Availability Impact: High
For more information on CVSS3 Scores, click here.Type: Upgrade version
Origin: GHSA-37ch-88jc-xwx2
Release Date: 2026-03-26
Fix Resolution: path-to-regexp - 0.1.13