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 20.6th 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).
Deeper analysis
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.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8455
Vulnerability details
Incorrect boundary conditions in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 148 and Thunderbird 148.
- CWE(s)
Related Threats
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.
CVEs Like This One
Affected Assets
Mitigating Controls
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.
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