CVE-2026-9358: postcss-selector-parser allows denial of service through uncontrolled AST recursion

A vulnerability was determined in postcss-selector-parser before 6.1.3 and 7.1.1. Affected is the function toString of the file src/selectors/container.js of the component AST Serialization. Executing a manipulation can lead to uncontrolled recursion. It is possible to launch the attack remotely. The exploit has been publicly disclosed and may be utilized. The vendor explains, that according to his definition “DoS on server-side on user-generated CSS is low risk for us (since most users compile own CSS with PostCSS).”