---
id: "CVE-2026-119331"
kind: "vulnerability"
aliases: ["CVE-2026-119331"]
title: "Ladybird browser: cross-origin stylesheets readable and editable by malicious pages"
severity: "high"
cvss: 7.1
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["browser", "ladybird", "other"]
not_affected_if: ["fixed-build"]
published_at: "2026-10-30T20:17:07+00:00"
first_seen_at: "2026-10-30T20:25:38+00:00"
updated_at: "2026-10-30T20:26:42+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-119331", "first_seen_at": "2026-10-30T20:25:38+00:00"}]
---

# Ladybird browser: cross-origin stylesheets readable and editable by malicious pages

Ladybird's CSSStyleSheet rule access (cssRules, insertRule, deleteRule) skipped the origin check for cross-origin stylesheets loaded without CORS. A malicious page can read those stylesheets' rules and insert or delete rules in a victim stylesheet, bypassing the Same-Origin Policy.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check whether your Ladybird build includes commit `c0d68bddf3e3616e5173835f0f4c155ee9700d91`.

## Fix

- Ladybird: use a build that includes commit `c0d68bddf3e3616e5173835f0f4c155ee9700d91`.

## Timeline

- 2026-10-30T20:25:38+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-119331

## From the sources

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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