CVE-2026-73646: PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
PostCSSto a version that resolves this vulnerability.Fixed in 8.5.18
Event History
Frequently Asked Questions
What is the severity of CVE-2026-73646?
CVE-2026-73646 has a severity rating of 7.5, categorized as high.
How do I fix CVE-2026-73646?
To fix CVE-2026-73646, upgrade to PostCSS version 8.5.18 or later.
What type of vulnerability is CVE-2026-73646?
CVE-2026-73646 is a path traversal vulnerability that can lead to arbitrary .map file disclosure.
Which software is affected by CVE-2026-73646?
CVE-2026-73646 affects the PostCSS library prior to version 8.5.18.
What does the path traversal vulnerability in CVE-2026-73646 allow?
The path traversal vulnerability in CVE-2026-73646 allows an attacker to disclose sensitive .map files.