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CVE-2026-41305

CVE-2026-41305 · PostCSS has XSS via Unescaped </style> in its CSS Stringify Output

This page contains facts from public vulnerability sources. Check the original advisory before updating.

PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. Versions prior to 8.5.10 do not escape `</style>` sequences when stringifying CSS ASTs. When user-submitted CSS is parsed and re-stringified for embedding in HTML `<style>` tags, `</style>` in CSS values breaks out of the style context, enabling XSS. Version 8.5.10 fixes the issue.

CVSS 6.1 · Medium · EPSS 0.2% · Fix available

Published
Updated

Stack: system · node

Affected products and versions

  • postcss

    Versions
    • < 8.5.10: Affected

    No fix published

  • node-postcss Debian:12

    Versions
    • 8.4.20+~cs8.0.23-1
    • 8.4.20+~cs8.0.23-1+deb12u1
    • 8.4.31+~cs8.0.26-1
    • 8.4.39+~cs9.2.29-1
    • 8.4.49+~cs9.2.32-1
    • 8.5.12+~cs9.3.32-1
    • 8.5.14+~cs9.3.34-1
    • 8.5.15+~cs9.3.34-1
    • 8.5.15+~cs9.3.38-1
    • 8.5.15+~cs9.3.39-1
    • 8.5.19+~cs10.2.23-1
    • 8.5.21+~cs10.2.23-1
    • 8.5.23+~cs10.2.23-1
    • 8.5.25+~cs10.2.23-1
    • 8.5.26+~cs10.2.24-1
    • 8.5.28+~cs10.2.24-1
    • 8.5.6+~cs9.3.28-1
    • 8.5.8+~cs9.3.30-1
    • 8.5.9+~cs9.3.30-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-postcss Debian:13

    Versions
    • 8.4.49+~cs9.2.32-1
    • 8.5.12+~cs9.3.32-1
    • 8.5.14+~cs9.3.34-1
    • 8.5.15+~cs9.3.34-1
    • 8.5.15+~cs9.3.38-1
    • 8.5.15+~cs9.3.39-1
    • 8.5.19+~cs10.2.23-1
    • 8.5.21+~cs10.2.23-1
    • 8.5.23+~cs10.2.23-1
    • 8.5.25+~cs10.2.23-1
    • 8.5.26+~cs10.2.24-1
    • 8.5.28+~cs10.2.24-1
    • 8.5.6+~cs9.3.28-1
    • 8.5.8+~cs9.3.30-1
    • 8.5.9+~cs9.3.30-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-postcss Debian:14

    Versions
    • 8.4.49+~cs9.2.32-1
    • 8.5.6+~cs9.3.28-1
    • 8.5.8+~cs9.3.30-1
    • 8.5.9+~cs9.3.30-1
    Affected ranges
    • ECOSYSTEM: < 8.5.12+~cs9.3.32-1

    Update to 8.5.12+~cs9.3.32-1

  • postcss npm

    Affected ranges
    • SEMVER: < 8.5.10

    Update to 8.5.10

  • node-postcss Ubuntu:20.04:LTS

    Versions
    • 6.0.23-1
    • 6.0.23-3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-postcss Ubuntu:22.04:LTS

    Versions
    • 8.2.1+~cs5.3.23-8
    • 8.4.5+~cs7.1.51-2
    • 8.4.6+~cs7.3.21-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-postcss Ubuntu:24.04:LTS

    Versions
    • 8.4.20+~cs8.0.23-1
    • 8.4.31+~cs8.0.26-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-postcss Ubuntu:25.10

    Versions
    • 8.4.49+~cs9.2.32-1
    • 8.5.6+~cs9.3.28-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-postcss Ubuntu:26.10

    Versions
    • 8.5.8+~cs9.3.30-1
    • 8.5.15+~cs9.3.34-1
    • 8.5.15+~cs9.3.38-1
    • 8.5.15+~cs9.3.39-1build1
    • 8.5.25+~cs10.2.23-1
    • 8.5.26+~cs10.2.24-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-postcss Ubuntu:26.04:LTS

    Versions
    • 8.5.6+~cs9.3.28-1
    • 8.5.8+~cs9.3.30-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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