CVE-2026-2796
Published: 24 February 2026
Summary
CVE-2026-2796 is a critical-severity Type Confusion (CWE-843) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Drive-by Compromise (T1189); ranked at the 45.6th 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 SC-39 (Process Isolation) and SI-16 (Memory Protection).
Deeper analysis
CVE-2026-2796 is a JIT miscompilation vulnerability in the JavaScript: WebAssembly component of Mozilla Firefox and Thunderbird. This flaw, classified under CWE-843 (incorrect type conversion or cast), allows for improper handling during just-in-time compilation of WebAssembly code, potentially leading to exploitable memory corruption. It affects versions of Firefox and Thunderbird prior to 148 and carries a CVSS v3.1 base score of 9.8, indicating critical severity due to its high impact on confidentiality, integrity, and availability.
A remote attacker can exploit this vulnerability over the network with low attack complexity, requiring no privileges, user interaction, or scope changes. By crafting malicious WebAssembly content deliverable via a website or other network-accessible vector, the attacker could trigger the miscompilation, enabling arbitrary code execution within the browser's sandboxed JavaScript engine. Successful exploitation would grant high-impact control over the affected process, potentially compromising the victim's system if chained with sandbox escapes.
Mozilla addressed this issue in Firefox 148 and Thunderbird 148, as detailed in security advisories MFSA 2026-13 and MFSA 2026-16, along with the upstream bug report at Bugzilla ID 2013165. Security practitioners should prioritize updating affected browsers to these patched versions and monitor for similar JIT-related issues in WebAssembly implementations.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8449
Vulnerability details
JIT miscompilation 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?
CVE enables drive-by compromise (T1189) and client-side exploitation (T1203) via malicious WebAssembly served over the network to achieve RCE in the browser process.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Timely flaw remediation requires patching the JIT miscompilation vulnerability in Firefox and Thunderbird versions prior to 148, directly eliminating the exploitable WebAssembly code execution.
Memory protection controls like ASLR and DEP prevent unauthorized code execution from the memory corruption caused by the WebAssembly JIT miscompilation.
Process isolation enforces browser sandboxing to contain arbitrary code execution within the JavaScript engine, limiting damage from the JIT miscompilation exploit.