CVE-2026-73646
PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure
No known exploitation. EPSS puts it in the 45th percentile. No fix published yet.
No public exploit knownFixNone yetNo fix or workaround published
e.g. OID 1.3.6.1.4.1.25623.1.0.190155
What to do
No fixed build or workaround is published yet. Limit exposure and watch for a patch.
- PostcssAffected: < 8.5.18Upgrade to: not statedStated by: CVE record
Versions as the sources state them. Full version matrix after sign-in
Steps
Written by AI from the record- Check whether your applications use PostCSS before 8.5.18 and process CSS supplied by users, customers, plugins, or external sources.
- Upgrade PostCSS to version 8.5.18 or later.
- Until upgraded, disable source-map processing for untrusted CSS by setting
map: falseand prevent untrusted CSS from reaching your build or processing service.
npm install postcss@8.5.18What it is
From the CVE record
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.
In plain language
Written by AI from the recordPostCSS versions before 8.5.18 can expose contents of map files when processing untrusted CSS, so businesses that accept CSS uploads or third-party CSS should update.
Unauthenticated path traversal (CWE-22) in PostCSS previous source-map auto-loading allows attacker-controlled sourceMappingURL values to read reachable .map files and return their sourcesContent.
If you're affected
- Source-code disclosure
- Configuration data exposure
- Sensitive file exposure
- Third-party upload risk
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
0.5% chance of exploitation activity in the next 30 days, which ranks it in the 45th percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
6 events over 32 days, from the signal feeds we watch.
- OpenVAS check addedrecord updated
- Publishedweakness classified, att&ck mapped, record updated
Affected products
Technical detail
CVSS 3.1 vector
Open in the CVSS calculatorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Scored 7.5 by NVD.
How it is reached
- Attack Vector NetworkExploitable remotely over the network without any special conditions
- Attack Complexity LowNo special conditions — the attack can be reliably reproduced
- Privileges Required NoneNo authentication required — anyone can exploit this
- User Interaction NoneNo user interaction needed — fully automated exploitation
Scope
- Scope UnchangedImpact is limited to the vulnerable component itself
Impact if exploited
- Confidentiality HighTotal information disclosure — all data in the component is compromised
- Integrity NoneNo integrity impact
- Availability NoneNo availability impact
Weaknesses
ATT&CK techniques
Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.
Sources
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