CVE-2026-117954

A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Use-after-free in the Layout: Positioned 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 isolate browser rendering processes and prevent memory corruption in the Layout: Positioned component when processing untrusted layout structures: upgrade to Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6 (or the corresponding fixed Red Hat builds), which resolves a use-after-free memory safety defect in the Layout: Positioned component, closing rendering crafted HTML/CSS content with positioned layout elements. Until patched, this is a concern on clients rendering untrusted web content or emails across all supported platforms, so restrict user interaction with untrusted or compromised web pages and email messages in affected client software. As a compensating measure, maintain Address Space Layout Randomization to randomize browser process memory layout and hinder reliable code execution. 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)