CVE-2026-117876

A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Use-after-free in the Layout: Text and Fonts 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 remediate memory lifetime management in the Layout: Text and Fonts component to prevent use-after-free corruption during text and font rendering: 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 condition in the Layout: Text and Fonts component during font and text layout processing, closing all 2 injection vectors (crafted web page rendering, crafted HTML content). Until patched, this is a concern on Any system running Firefox or Thunderbird loading untrusted web pages or HTML messages, so Restrict users from loading untrusted web pages and opening untrusted HTML email messages. As a compensating measure, Enable Address Space Layout Randomization to randomize process memory layout and hinder reliable address prediction during memory exploitation. 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-101 ASLR (Address Space Layout Randomization) (medium)