CVE-2026-2787
Published: 24 February 2026
Summary
CVE-2026-2787 is a critical-severity Use After Free (CWE-416) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 5.8th 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 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly remediates the use-after-free vulnerability by requiring timely identification, reporting, and patching of affected Firefox and Thunderbird versions as specified in Mozilla advisories.
Monitors and scans for known vulnerabilities like CVE-2026-2787 in browser components, enabling detection of vulnerable versions and prompt remediation.
Implements memory protection mechanisms such as ASLR and DEP that mitigate exploitation of the use-after-free vulnerability through memory corruption defenses.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Use-after-free in browser DOM component enables remote unauthenticated arbitrary code execution (with sandbox escape potential) in client applications like Firefox/Thunderbird, directly matching Exploitation for Client Execution.
NVD Description
Use-after-free in the DOM: Window and Location component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
Deeper analysisAI
CVE-2026-2787 is a use-after-free vulnerability (CWE-416) in the DOM Window and Location component, affecting Mozilla Firefox and Thunderbird browsers. It impacts versions prior to Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8. The vulnerability was publicly disclosed on February 24, 2026, and carries a CVSS v3.1 base score of 9.8, indicating critical severity.
The vulnerability can be exploited remotely over the network by unauthenticated attackers with low complexity and no user interaction required. Successful exploitation grants high-impact access to confidentiality, integrity, and availability, potentially allowing arbitrary code execution within the browser's context, such as memory corruption leading to sandbox escape or full compromise of the affected application.
Mozilla's security advisories (MFSA2026-13 through MFSA2026-16) and the associated Bugzilla entry detail the patch, recommending immediate upgrades to the fixed versions: Firefox 148, Firefox ESR 115.33 or 140.8, Thunderbird 148, or Thunderbird 140.8. No workarounds are specified beyond applying these updates.
Details
- CWE(s)