CVE-2026-4693 is a vulnerability caused by incorrect boundary conditions in the Audio/Video Playback component of Mozilla Firefox. This vulnerability was addressed and fixed in Firefox 149, Firefox ESR 115.34, and Firefox ESR 140.9, as well as corresponding Thunderbird versions. The CVSS v3.1 base score is 7.5, indicating high severity, with an attack vector of network, low attack complexity, no privileges required, no user interaction, and impact limited to availability (denial-of-service). The vulnerability is part of a set of memory safety issues fixed in these releases. The vendor advisories confirm the fix availability and provide detailed bug references.

The vulnerability can cause denial-of-service (availability impact) in affected Firefox versions due to incorrect boundary conditions in the Audio/Video Playback component. There is no confirmed impact on confidentiality or integrity. No known exploits in the wild have been reported. Successful exploitation could disrupt normal browser operation, potentially causing crashes or hangs.

Mozilla has released official fixes for this vulnerability in Firefox 149, Firefox ESR 115.34, and Firefox ESR 140.9. Users and administrators should update to these or later versions to remediate the issue. Since the vulnerability is fixed in these releases, no additional mitigation steps are required beyond applying the official updates. Patch status is confirmed by Mozilla advisories.