Ladybird: Missing origin-clean enforcement in CSSStyleSheet allows cross-origin CSS read and mutation

Description

Ladybird is a truly independent web browser. Prior to the c0d68bddf3e3616e5173835f0f4c155ee9700d91 commit, CSSStyleSheet.cssRules, insertRule(), and deleteRule() in Libraries/LibWeb/CSS/CSSStyleSheet.cpp did not enforce the stylesheet origin-clean flag with the required SecurityError, even though cross-origin imported stylesheets were correctly marked non-origin-clean. A malicious page could read parsed rules from a stylesheet loaded without CORS and could insert or delete rules in the victim stylesheet, bypassing the Same-Origin Policy. Reading could expose selectors, generated content, feature markers, or other sensitive rule text, while mutation could alter page visibility or layout. The issue does not provide memory corruption, code execution, or persistence after the attacker page closes. This vulnerability is fixed by commit c0d68bddf3e3616e5173835f0f4c155ee9700d91.

Scores

EPSS (exploitation in 30 days)

0.18% · top 92% of all CVEs (5 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.1.

Weakness

• CWE-200: Exposure of Sensitive Information to an Unauthorized Actor (opens in a new tab)All about CWE-200 and its CVEs
• CWE-346: Origin Validation Error (opens in a new tab)All about CWE-346 and its CVEs

Affected products

• LadybirdBrowser · ladybird

  • affected < c0d68bddf3e3616e5173835f0f4c155ee9700d91

References (2)

• https://github.com/LadybirdBrowser/ladybird/security/advisories/GHSA-xj66-c4cw-xwh3 (opens in a new tab)x_refsource_CONFIRM
• https://github.com/LadybirdBrowser/ladybird/commit/c0d68bddf3e3616e5173835f0f4c155ee9700d91 (opens in a new tab)x_refsource_MISC

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-119331](https://trackcve.app/badge/CVE-2026-119331.svg)](https://trackcve.app/cve/CVE-2026-119331)

Record last updated 30 Oct 2026, 22:14 UTC.