CVE-2026-2801
Published: 24 February 2026
Summary
CVE-2026-2801 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 18.6th 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 mitigates the CVE by requiring timely identification, prioritization, and remediation of the WebAssembly boundary condition flaw through patching to Firefox/Thunderbird 148.
Ensures organizations monitor and implement vendor security advisories like Mozilla's MFSA 2026-13/16 to apply patches addressing this vulnerability.
Enables scanning and monitoring to identify systems running vulnerable Firefox/Thunderbird versions affected by the WebAssembly boundary check flaw.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Vulnerability enables remote exploitation of a client application (browser/mail) to cause a crash/DoS with no user interaction or privileges required, directly mapping to application/system exploitation for endpoint denial of service.
NVD Description
Incorrect boundary conditions in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 148 and Thunderbird 148.
Deeper analysisAI
CVE-2026-2801 is a vulnerability involving incorrect boundary conditions in the JavaScript WebAssembly component of Mozilla Firefox and Thunderbird. It affects versions prior to Firefox 148 and Thunderbird 148, where improper handling of boundary checks in WebAssembly processing can lead to issues. The vulnerability 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 can exploit this vulnerability over the network with low complexity, requiring no privileges or user interaction. Successful exploitation results in high-impact denial of service, potentially crashing the affected browser or mail client without compromising confidentiality or integrity.
Mozilla's security advisories (MFSA 2026-13 and MFSA 2026-16) and the associated Bugzilla entry (bug 2009901) confirm the issue was addressed in Firefox 148 and Thunderbird 148. Security practitioners should ensure users update to these patched versions to mitigate the risk.
Details
- CWE(s)