CVE-2026-6746 is a use-after-free vulnerability classified under CWE-416 affecting the DOM: Core & HTML component in Mozilla Firefox and Thunderbird. This memory safety issue could allow an attacker to cause a denial-of-service (crash) due to improper handling of memory after it has been freed. The vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10 as documented in Mozilla security advisories MFSA 2026-30 and MFSA 2026-31. The CVSS v3.1 base score is 7.5 with vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, indicating network attack vector, low attack complexity, no privileges or user interaction required, unchanged scope, no confidentiality or integrity impact, but high impact on availability.

The vulnerability allows remote attackers to cause a denial-of-service (application crash) by exploiting a use-after-free condition in the DOM: Core & HTML component. There is no reported impact on confidentiality or integrity. No known exploits in the wild have been reported. The high CVSS score reflects the potential for significant disruption of service if exploited.

This vulnerability has been fixed by Mozilla in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10. Users and administrators should update to these versions or later to remediate the issue. No additional mitigation steps are required as the fix is officially released and available.