CVE-2026-4697
Published: 24 March 2026
Summary
CVE-2026-4697 is a high-severity Improper Check for Unusual or Exceptional Conditions (CWE-754) vulnerability in Mozilla Firefox. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 48.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).
Deeper analysis
CVE-2026-4697 involves incorrect boundary conditions (CWE-754) in the Audio/Video: Web Codecs component of Mozilla products. This vulnerability affects Firefox, Firefox ESR, and Thunderbird, with fixes released in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
The vulnerability carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Remote attackers with no privileges or user interaction can exploit it over the network with low attack complexity, achieving a high impact on availability through denial of service, such as application crashes, without compromising confidentiality or integrity.
Mozilla's security advisories MFSA 2026-20, MFSA 2026-22, MFSA 2026-23, and MFSA 2026-24, along with Bugzilla entry 2020422, provide further details on the issue and patches. Security practitioners should ensure affected systems update to the specified fixed versions for mitigation.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14812
Vulnerability details
Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability allows remote network exploitation of a client-side boundary condition flaw in web codecs, directly causing application crashes and high availability impact with no privileges or user interaction required, mapping precisely to application/system exploitation for endpoint DoS.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely identification, testing, and application of patches to remediate the specific boundary condition flaw in the Web Codecs component of Firefox and Thunderbird.
Mandates vulnerability scanning to identify systems running vulnerable versions of Mozilla products affected by CVE-2026-4697.
Implements controls to limit or detect the effects of denial-of-service attacks exploiting this vulnerability to cause application crashes.
Hardening callouts derived
Configuration rules from DISA STIG baselines that reduce the attack surface for weaknesses of the type cited by this CVE. Derived transitively via CVE→CWE→STIG over `controls_xwalks` (authoritative rows only).
Oracle Linux 8 (3 rules)
- V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. via CWE-754
- V-248573 The OL 8 file integrity tool must notify the system administrator (SA) when changes to the baseline configuration or anomalies in the operation of any security functions are discovered within an organizationally defined frequency. via CWE-754
- V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. via CWE-754
Oracle Linux 9 (1 rule)
- V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. via CWE-754