CVE-2026-4714
Published: 24 March 2026
Summary
CVE-2026-4714 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 6.2th 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).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly requires timely remediation of flaws like incorrect boundary conditions in Firefox/Thunderbird by applying patches to fixed versions such as Firefox 149.
Provides denial-of-service protections that mitigate the availability disruption from remote exploitation causing browser crashes.
Enables vulnerability scanning to identify systems running vulnerable versions of Firefox or Thunderbird prior to exploitation.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote unauthenticated exploit of boundary condition flaw in client application (Firefox/Thunderbird) directly enables crash-based availability impact, matching Endpoint DoS via Application or System Exploitation.
NVD Description
Incorrect boundary conditions in the Audio/Video component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Deeper analysisAI
CVE-2026-4714 is a vulnerability stemming from incorrect boundary conditions (CWE-754) in the Audio/Video component of Mozilla Firefox and Thunderbird. It affects versions prior to Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. The issue 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), indicating high severity primarily due to its potential for availability disruption.
Attackers can exploit this vulnerability remotely over the network with low complexity, requiring no privileges, authentication, or user interaction. Successful exploitation leads to denial-of-service impacts, such as crashing the affected browser or mail client, without compromising confidentiality or integrity.
Mozilla's security advisories (MFSA 2026-20, 22, 23, and 24) and the associated Bugzilla entry (bug 2018126) confirm the vulnerability was addressed in the specified fixed releases. Security practitioners should ensure users upgrade to Firefox 149 or later, Firefox ESR 140.9 or later, Thunderbird 149 or later, and Thunderbird 140.9 or later to mitigate the risk.
Details
- CWE(s)