CVE-2026-117860

A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Same-origin policy bypass in the DOM: Navigation 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 enforce strict same-origin policy validation within the DOM: Navigation component to block cross-origin DOM access: upgrade to Firefox 159, Firefox ESR 153.6, and Thunderbird 159 (or the corresponding fixed Red Hat builds), which enforces origin checks during DOM navigation to prevent cross-origin policy bypasses, closing all 2 injection vectors (crafted web page navigation, cross-origin DOM manipulation). Until patched, this is a concern on All platforms running vulnerable Firefox or Thunderbird web-rendering contexts, so Restrict users from following untrusted links or visiting untrusted websites until the browser is updated. These controls limit blast radius and contain exploitation, but they do not fix the underlying same-origin policy bypass — apply the upstream patch to fully remediate.