CVE-2026-117887

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 execution against dangling DOM pointers by isolating or blocking untrusted DOM and HTML rendering in Firefox: upgrade to Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6 (or the corresponding fixed Red Hat builds), which corrects memory management and object lifecycle handling in the DOM: Core & HTML component to prevent use-after-free conditions, closing all 2 injection vectors (crafted web page, crafted HTML document). Until patched, this is a concern on Users processing untrusted web content or viewing untrusted HTML documents across all supported platforms, so Prevent users from visiting untrusted websites or opening unverified HTML documents in the browser. As a compensating measure, Maintain ASLR to randomize browser memory layout, making reliable code execution via dangling DOM pointers significantly harder, Enforce Full RELRO and PIE to keep binary segments and GOT entries randomized and read-only, impeding control-flow hijacking, and Operate SELinux in enforcing mode to confine the browser process and limit lateral movement or system access if exploitation occurs. 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)