CVE-2026-117881

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 (2026-11-02) --- 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 prevent dereferencing of freed memory in the DOM: Core & HTML component during HTML object lifecycle management: upgrade to Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6 (or the corresponding fixed Red Hat builds), which resolves the use-after-free vulnerability in the DOM: Core & HTML component, closing all 2 injection vectors (crafted web page, crafted HTML content). Until patched, this is a concern on all platforms running affected Firefox installations, so restrict user browsing to trusted websites and prevent loading untrusted or external HTML documents. As a compensating measure, enable ASLR to randomize browser process memory layout and hinder predicting target function and shellcode addresses, enforce full RELRO and PIE to ensure position-independent executable code and keep the Global Offset Table read-only, and keep SELinux in enforcing mode to confine the Firefox process to least-privilege domains and limit post-exploitation host compromise. These controls limit blast radius and contain exploitation, but they do not fix the underlying use-after-free defect — apply the upstream patch to fully remediate.

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