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.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-r28c-9q8g-f849 PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Mon, 17 Aug 2026 16:45:00 +0000

Type Values Removed Values Added
First Time appeared Postcss
Postcss postcss
Vendors & Products Postcss
Postcss postcss

Mon, 17 Aug 2026 15:45:00 +0000

Type Values Removed Values Added
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.
Title PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure
Weaknesses CWE-22
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-08-17T16:36:37.422Z

Reserved: 2026-08-13T14:04:09.604Z

Link: CVE-2026-73646

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-17T16:17:47.257

Modified: 2026-08-17T16:17:47.257

Link: CVE-2026-73646

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-17T16:30:06Z

Weaknesses