CVE-2026-2767
Published: 24 February 2026
Summary
CVE-2026-2767 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 17.5th 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-16 (Memory Protection) 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 in Firefox and Thunderbird's WebAssembly component through timely patching to the fixed versions (Firefox 148, ESR 140.8, Thunderbird 148/140.8).
Implements memory protection mechanisms like ASLR, DEP, and stack canaries that prevent successful exploitation of use-after-free errors in the JavaScript WebAssembly component.
Facilitates rapid awareness and response to Mozilla security advisories (MFSA 2026-13, 15, 16, 17) and Bugzilla updates for this critical CVE, enabling flaw remediation.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Use-after-free in client-side JS/WebAssembly engine enables remote arbitrary code execution in browser/email client with no user interaction or auth, directly matching Exploitation for Client Execution.
NVD Description
Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
Deeper analysisAI
CVE-2026-2767 is a use-after-free vulnerability (CWE-416) in the JavaScript WebAssembly component of Mozilla products. It affects Firefox versions prior to 148, Firefox ESR prior to 140.8, Thunderbird prior to 148, and Thunderbird prior to 140.8. The vulnerability carries a CVSS v3.1 base score of 9.8, indicating critical severity due to its network accessibility, low attack complexity, lack of required privileges or user interaction, and high impacts on confidentiality, integrity, and availability.
Remote attackers can exploit this vulnerability over the network without authentication or user interaction by crafting malicious WebAssembly content loaded in a browser or email client. Successful exploitation could lead to arbitrary code execution, potentially allowing full compromise of the affected application and access to sensitive data or system resources within the user's context.
Mozilla's security advisories (MFSA 2026-13, 15, 16, and 17) and the associated Bugzilla entry (bug 2013741) confirm the issue was addressed in the specified fixed releases. Security practitioners should prioritize updating affected Firefox and Thunderbird installations to mitigate the risk, as no workarounds are detailed in the provided references.
Details
- CWE(s)