CVE-2026-117916

A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Use-after-free in the XSLT 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 processing and rendering of untrusted XSLT stylesheets or documents within browser and mail client rendering engines: upgrade to Firefox 159, Firefox ESR 153.6, and Thunderbird 159 (or the corresponding fixed Red Hat builds), which resolves the use-after-free condition within the XSLT component during stylesheet or document processing, closing crafted XSLT stylesheet processing. Until patched, this is a concern on users and environments processing untrusted web content or XSLT documents in Firefox or Thunderbird across all platforms, so avoid loading untrusted web pages and block rendering of untrusted XSLT stylesheets or documents. As a compensating measure, Ensure Address Space Layout Randomization is active to randomize process memory addresses and hinder predicting memory offsets needed to hijack control flow. These controls limit blast radius and contain exploitation, but they do not fix the underlying XSLT use-after-free defect — apply the upstream patch to fully remediate.

Highest-impact CME: CME-101 ASLR (Address Space Layout Randomization) (medium)