CVE-2026-73646

HIGH 7.5

PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-22
Vendor	postcss
Product	postcss
Published	Aug 17, 2026
Last Updated	Aug 17, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Affected Versions

postcss / postcss

< 8.5.18

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/postcss/postcss/security/advisories/GHSA-r28c-9q8g-f849 github.com: https://github.com/postcss/postcss/commit/95663d3eb7ba26f4854dd19d3b4f4425760cf56c github.com: https://github.com/postcss/postcss/releases/tag/8.5.18