Ladybird: Missing origin-clean enforcement in CSSStyleSheet allows cross-origin CSS read and mutation
Impact
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,…
Source excerpt · GitHub_MAffected packages
Affected products
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LadybirdBrowser · GitHub_M
ladybird
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LadybirdBrowser · GitHub_M
ladybird
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affected
< c0d68bddf3e3616e5173835f0f4c155ee9700d91
Other versions: unknown
Original source 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.
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Evidence available
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Original records
CVE-2026-119331View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.
cve.new JSON →Underlying weaknesses
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Contributing organizations · 2
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What changed
Follow changes- CVE · CVE-2026-119331
Observed 2026-10-30T22:40:44.124Z · upstream updated 2026-10-30T22:14:59.829Z
Prioritization updated
before
[]
after
[ { "source": "CISA-ADP", "type": "SSVC", "role": "CISA Coordinator", "timestamp": "2026-10-30T21:18:16.293042Z", "decisions": [ { "name": "Exploitation", "value": "none" }, { "name": "Automatable", "value": "no" }, { "name": "Technical Impact", "value": "partial" } ] } ]
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