CVE-2026-69153 PostCSS: incomplete fix of GHSA-6g55-p6wh-862q — attacker-controlled sourceMappingURL reads arbitrary .map files when `from` is unset

What is CVE-2026-69153?

CVE-2026-69153 is a medium-severity path traversal vulnerability in postcss, published on 3 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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 8.5.19, if from is unset, an attacker can cause PreviousMap.loadFile() to read an unintended source-map file by supplying an absolute or directory-traversal sourceMappingURL. The resulting map’s sources and sourcesContent may then be exposed to the application. This issue is fixed in version 8.5.19.

Weakness: CWE-22, CWE-200

Which versions are affected by CVE-2026-69153?

2 open source packages ship an affected version, including postcss. It affects 1 product.

Products include Postcss Postcss.

How do I fix CVE-2026-69153?

Upgrade postcss to 8.5.23 or later.

Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.

Is CVE-2026-69153 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-69153 exists.

Other vulnerabilities in postcss

• CVE-2026-45623 PostCSS: Arbitrary file read and information disclosure via attacker-controlled sourceMappingURL in CSS comments High 7.5
• CVE-2023-44270 PostCSS line return parsing error Medium 5.3
• CVE-2021-23382 Regular Expression Denial of Service (ReDoS) Medium 5.3
• CVE-2021-23368 Regular Expression Denial of Service (ReDoS) Medium 5.3

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as CLEANSTART-2026-PI70585, CLEANSTART-2026-SY59629, CLEANSTART-2026-WU05348, CLSA-2026-1790190219, CLSA-2026-1790200936, CLSA-2026-1790202643 and 19 more.