CVE-2026-117941

A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Use-after-free in the DOM: CSS Object Model component

Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

--- CME Mitigation Guidance (2026-11-02) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.

The highest-value action is to disable or restrict JavaScript execution to prevent scripted DOM and CSS Object Model manipulations in the browser: upgrade to Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6 (or the corresponding fixed Red Hat builds), which resolves the use-after-free condition during DOM CSS Object Model (CSSOM) processing, closing crafted CSS Object Model manipulation via malicious web page. Until patched, this is a concern on Users rendering untrusted HTML/CSS content or visiting untrusted web pages in Firefox or Thunderbird across any platform, so Restrict users from navigating to untrusted websites or opening untrusted HTML and CSS content in Firefox and Thunderbird. As a compensating measure, Ensure Address Space Layout Randomization is active to randomize browser memory layout and require an additional information leak and Disable or restrict JavaScript execution to block scripted DOM and CSS Object Model manipulations required to trigger and groom the flaw. These controls limit blast radius and contain exploitation, but they do not fix the underlying DOM CSS Object Model use-after-free defect — apply the upstream patch to fully remediate.

Highest-impact CME: CME-1309 Script Engine Restriction (Sandbox / Disable) (medium)