CVE-2026-4693
Published: 24 March 2026
Summary
CVE-2026-4693 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 SC-5 (Denial-of-service Protection).
Deeper analysis
CVE-2026-4693 is a vulnerability involving incorrect boundary conditions in the Audio/Video: Playback component of Mozilla Firefox and Thunderbird. It affects versions of Firefox prior to 149, Firefox ESR prior to 115.34 and 140.9, and Thunderbird prior to 149 and 140.9. The issue is classified under CWE-754 (Improper Check for Unusual or Exceptional Conditions) and carries a CVSS v3.1 base score of 7.5.
Remote attackers require no privileges or user interaction to exploit this vulnerability over the network with low complexity. Successful exploitation results in a denial-of-service condition due to high availability impact, with no effects on confidentiality or integrity.
Mozilla security advisories (MFSA 2026-20 through 2026-23) and the associated Bugzilla entry detail the fix applied in the specified versions of Firefox and Thunderbird, recommending immediate upgrades to patched releases for mitigation.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14808
Vulnerability details
Incorrect boundary conditions in the Audio/Video: Playback component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote unauthenticated network exploitation of boundary condition flaw in media playback directly enables application/system crash for DoS impact (T1499.004).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Mandates timely identification, reporting, and patching of flaws like the incorrect boundary conditions in Firefox's Audio/Video Playback component to prevent remote DoS exploitation.
Requires robust error handling for exceptional conditions during media playback to avoid crashes and denial-of-service from CWE-754 boundary issues.
Limits the effects of and detects denial-of-service events resulting from exploitation of the high availability impact vulnerability in the playback component.
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
Windows 10 (1 rule)
- V-220726 Data Execution Prevention (DEP) must be configured to at least OptOut. via CWE-823
Windows 11 (1 rule)
- V-253283 Data Execution Prevention (DEP) must be configured to at least OptOut. via CWE-823