CVE-2026-69153

A flaw was found in PostCSS. A remote attacker can exploit this vulnerability by providing a specially crafted sourceMappingURL when a specific configuration (the 'from' parameter) is not set. This can cause the application to read and expose unintended source-map files, potentially revealing sensitive information about the application's source code.

Red Hat rates this flaw as Moderate because the information disclosed is limited to files with a .map extension. Source map files may contain source code paths and content, but the attacker cannot read arbitrary files on the system. Exploitation requires the application to process attacker-controlled CSS through PostCSS on the server side.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Pass map: false when invoking PostCSS to disable source map auto-loading. This prevents the path traversal from being triggered, though it removes source map support entirely.