CVE-2026-6771 is a mitigation bypass vulnerability affecting the DOM security component in Mozilla Firefox. It allows bypassing certain security mitigations implemented in the browser's DOM handling. The vulnerability was fixed in Firefox 150 and Firefox ESR 140.10 as part of Mozilla's April 2026 security updates. The fix is included in official Mozilla releases, and no known exploits in the wild have been reported. This vulnerability is one among many addressed in these updates, which also include memory safety bugs and other security issues.

The vulnerability could allow an attacker to bypass security mitigations in the DOM security component, potentially weakening the browser's defense mechanisms. However, no known exploits in the wild have been reported. The overall impact is assessed as moderate by Mozilla. Since the vulnerability is fixed in Firefox 150 and Firefox ESR 140.10, users running these or later versions are protected.

Users and administrators should update Mozilla Firefox to version 150 or later, or Firefox ESR to version 140.10 or later, to remediate this vulnerability. Mozilla has officially fixed this issue in these releases. No additional mitigation actions are required beyond applying the official update.