CVE-2026-117919

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 eliminate use-after-free conditions during DOM Core and HTML manipulation within the browser rendering engine: upgrade to Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6 (or the corresponding fixed Red Hat builds), which corrects object lifecycle management in the DOM: Core & HTML component to resolve the use-after-free flaw, closing all 2 injection vectors (crafted HTML content, malicious DOM manipulation script). Until patched, this is a concern on deployments rendering web content or opening untrusted HTML in Firefox or Thunderbird across supported platforms, so restrict user interaction with untrusted websites and prevent rendering of untrusted external web content. As a compensating measure, Ensure ASLR is enabled to randomize process memory layout and hinder reliable exploitation of heap corruption, Enforce Full RELRO and PIE binary protections to prevent GOT overwrite exploitation following heap corruption, and Run SELinux in enforcing mode to confine the browser process and restrict post-exploitation access on Linux. These controls limit blast radius and contain exploitation, but they do not fix the underlying DOM Core & HTML use-after-free defect — apply the upstream patch to fully remediate.

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