CVE-2026-117877

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 (2026-11-03) --- 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 use-after-free pointer dereferences during layout processing within the Text and Fonts component: upgrade to Firefox 159, Firefox ESR 153.6, Thunderbird 159 (or the corresponding fixed Red Hat builds), which fixes use-after-free memory corruption during layout processing in the Layout: Text and Fonts component, closing all 2 injection vectors (crafted web page, malicious text or font layout rendering). Until patched, this is a concern on users viewing web content in affected browsers or browser-like contexts across all platforms, so restrict user interaction with untrusted websites and avoid rendering untrusted web content in browser-like contexts. As a compensating measure, ensure Address Space Layout Randomization (ASLR) is active across browser processes to hinder reliable exploitation of memory corruption. These controls limit blast radius and contain exploitation, but they do not fix the underlying use-after-free flaw — apply the upstream patch to fully remediate.

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