CVE-2026-117900

A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Use-after-free in the DOM: Editor 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 the dereference or reuse of freed memory objects within the DOM Editor component during document editing and DOM manipulation: 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 condition in the DOM: Editor component during document editing and DOM manipulation, closing all 2 injection vectors (crafted web page triggering DOM editor manipulation, crafted HTML content in email or rich text editor). Until patched, this is a concern on Firefox and Thunderbird installations on all platforms processing untrusted web or rich text content, so restrict browsing untrusted websites and avoid opening or rendering untrusted HTML and rich text content in browser and email clients. As a compensating measure, randomize userland process address space using ASLR to hinder reliable code reuse or control-flow hijacking via dangling DOM objects, compile browser binaries with Full RELRO and PIE to enforce read-only relocations and position-independent execution, and run SELinux in enforcing mode to confine the browser process domain if arbitrary code execution occurs. These controls limit blast radius and contain exploitation, but they do not fix the underlying DOM Editor use-after-free defect — apply the upstream patch to fully remediate.

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