CVE-2026-117931

A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Use-after-free in the DOM: Events 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 dangling pointer reuse during DOM event processing in the DOM: Events component: 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 memory corruption condition within the DOM: Events component, closing all 2 injection vectors (crafted web page, crafted HTML email). Until patched, this is a concern on Users processing untrusted web pages or HTML emails in Firefox or Thunderbird on any supported platform, so Avoid opening untrusted web links and disable or restrict the rendering of untrusted HTML email content in browser and mail client sessions. As a compensating measure, Enable ASLR to randomize browser user-space memory layout and hinder reliable gadget chain resolution, Enforce Full RELRO and PIE to restrict exploitation targets after memory corruption, and Maintain SELinux in enforcing mode to confine browser and mail client processes to their mandatory access control domain. These controls limit blast radius and contain exploitation, but they do not fix the underlying DOM: Events use-after-free defect — apply the upstream patch to fully remediate.

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