LadybirdBrowser Ladybird CSS Stylesheet CSSStyleSheet.cpp insertRule/deleteRule cross-domain policy

Summaryinfo

A vulnerability described as problematic has been identified in LadybirdBrowser Ladybird. Affected by this issue is the function insertRule/deleteRule of the file Libraries/LibWeb/CSS/CSSStyleSheet.cpp of the component CSS Stylesheet. Executing a manipulation can lead to cross-domain policy. The identification of this vulnerability is CVE-2026-119331. The attack may be launched remotely. There is no exploit available. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability classified as problematic was found in LadybirdBrowser Ladybird (unknown version). This vulnerability affects the function insertRule/deleteRule of the file Libraries/LibWeb/CSS/CSSStyleSheet.cpp of the component CSS Stylesheet. The manipulation with an unknown input leads to a cross-domain policy vulnerability. The CWE definition for the vulnerability is CWE-942. The product uses a cross-domain policy file that includes domains that should not be trusted. As an impact it is known to affect confidentiality. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-119331 since 10/29/2026. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available.

Applying the patch c0d68bddf3e3616e5173835f0f4c155ee9700d91 is able to eliminate this problem.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• LadybirdBrowser

Name

• Ladybird

Website

• Product: https://github.com/LadybirdBrowser/ladybird/

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