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.
Published: 2026-08-17
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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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
History

Thu, 27 Aug 2026 18:00:00 +0000

Type Values Removed Values Added
First Time appeared Redhat
Redhat hummingbird
CPEs cpe:/a:redhat:hummingbird:1
Vendors & Products Redhat
Redhat hummingbird
References
Metrics threat_severity

None

threat_severity

Important


Mon, 17 Aug 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


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'}


Subscriptions

Postcss Postcss
Redhat Hummingbird
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

Updated: 2026-08-17T16:36:25.466Z

cve-icon NVD

Status : Received

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

Modified: 2026-08-17T17:16:51.660

Link: CVE-2026-73646

cve-icon Redhat

Severity : Important

Publid Date: 2026-08-17T15:35:13Z

Links: CVE-2026-73646 - Bugzilla

cve-icon OpenCVE Enrichment

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

Weaknesses