CVE-2026-4695
Published: 24 March 2026
Summary
CVE-2026-4695 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-11 (Error Handling) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-4695 is a vulnerability involving incorrect boundary conditions in the Audio/Video: Web Codecs component of Mozilla products. It affects Firefox, Firefox ESR, Thunderbird, and was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. The issue is classified under CWE-754 (Improper Check for Unusual or Exceptional Conditions) with a CVSS v3.1 base score of 7.5.
The vulnerability can be exploited remotely over the network (AV:N) with low attack complexity (AC:L), requiring no privileges (PR:N) or user interaction (UI:N), and without changing scope (S:U). Successful exploitation results in high-impact denial of service (A:H) with no impact on confidentiality or integrity, potentially causing application crashes.
Mozilla security advisories, including MFSA 2026-20, 2026-22, 2026-23, and 2026-24, along with Bugzilla entry 2020030, detail the patch deployments in the specified versions, recommending users update to these releases for mitigation.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14810
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 enables remote exploitation of improper boundary conditions in Web Codecs, directly causing application crashes and high-impact denial of service with no code execution, mapping to T1499.004 (Application or System Exploitation under Endpoint Denial of Service).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly remediates the boundary condition vulnerability by requiring timely identification, reporting, and patching to fixed versions like Firefox 149 and ESR 140.9.
Requires the system to generate no unhandled errors and manage exceptions without compromising availability, directly countering the crash-inducing improper boundary checks in Web Codecs.
Enforces validation of external inputs for length, range, and boundary conditions before processing in components like Audio/Video Web Codecs, mitigating exploitation vectors.
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