CVE-2026-6751 is a vulnerability classified under CWE-457 (Use of Uninitialized Variable) affecting the Audio/Video: Web Codecs component in Mozilla Firefox. The flaw involves uninitialized memory usage, which can result in memory corruption. The vulnerability has a CVSS v3.1 base score of 7.3 (high severity) with network attack vector, low attack complexity, no privileges required, and no user interaction needed. Mozilla fixed this vulnerability in Firefox 150 and Firefox ESR 140.10, as documented in their security advisories MFSA 2026-30 and MFSA 2026-32. The advisories confirm the presence of the vulnerability, its impact, and the availability of patches.

The vulnerability could allow an attacker to cause memory corruption by exploiting uninitialized memory in the Web Codecs component, potentially leading to information disclosure, integrity loss, or availability impact. However, no known exploits have been observed in the wild. The impact is rated high due to the potential for memory corruption and related security consequences.

Mozilla has released official fixes for this vulnerability in Firefox 150 and Firefox ESR 140.10. Users and administrators should update affected Firefox and Thunderbird installations to these versions or later 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 MFSA 2026-30 and MFSA 2026-32.