CVE-2026-117949

A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Use-after-free in the DOM: Core & HTML 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 (2026-11-03) --- 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 isolate or restrict rendering of untrusted web content to prevent triggering memory corruption in the DOM: Core & HTML component: upgrade to Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6 (or the corresponding fixed Red Hat builds), which resolves use-after-free memory corruption within the DOM: Core & HTML component, closing all 2 injection vectors (crafted web page, malicious HTML document). Until patched, this is a concern on systems running affected Firefox or Thunderbird deployments loading untrusted HTML content, so restrict user interaction to prevent navigating to untrusted websites or loading untrusted HTML documents. As a compensating measure, Enable Address Space Layout Randomization to randomize browser memory layout and require an additional address leak for code execution and Enforce SELinux in enforcing mode to confine the compromised Firefox process and bound filesystem access and payload execution. These controls limit blast radius and contain exploitation, but they do not fix the underlying DOM use-after-free defect — apply the upstream patch to fully remediate.

Highest-impact CME: CME-301 SELinux (Enforcing Mode) (medium)