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 34.8th 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-2026-4714 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.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14843
Vulnerability details
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.
- CWE(s)
Related Threats
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.
CVEs Like This One
Affected Assets
Mitigating Controls
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.
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