Vulnerability · Published Aug 17, 2026 · Assigned by GitHub_M
CVE-2026-73646PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure
High 7.5
In plain English
A high-severity path traversal in postcss from postcss. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 45% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. Prior to 8.5.18, lib/previous-map.js loadMap() passes attacker-controlled sourceMappingURL values to join(dirname(opts.from), annotation), and loadFile() permits traversed or absolute .map paths, allowing untrusted CSS processed without map: false to disclose sourcesContent from arbitrary reachable .map files through result.map. This issue is fixed in version 8.5.18.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | node-postcss | no fix listed | DEBIAN-CVE-2026-73646 |
| Debian:13 | node-postcss | no fix listed | DEBIAN-CVE-2026-73646 |
| Debian:14 | node-postcss | 8.5.19+~cs10.2.23-1 | DEBIAN-CVE-2026-73646 |
| Ubuntu:22.04:LTS | node-postcss | no fix listed | UBUNTU-CVE-2026-73646 |
| Ubuntu:24.04:LTS | node-postcss | no fix listed | UBUNTU-CVE-2026-73646 |
| Ubuntu:26.04:LTS | node-postcss | no fix listed | UBUNTU-CVE-2026-73646 |
| npm | postcss | 8.5.18 | GHSA-r28c-9q8g-f849 |
Affected products (as reported)
Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
References
- https://github.com/postcss/postcss/security/advisories/GHSA-r28c-9q8g-f849 x_refsource_CONFIRM
- https://github.com/postcss/postcss/commit/95663d3eb7ba26f4854dd19d3b4f4425760cf56c x_refsource_MISC
- https://github.com/postcss/postcss/releases/tag/8.5.18 x_refsource_MISC