CVE-2026-2793
Published: 24 February 2026
Summary
CVE-2026-2793 is a critical-severity Out-of-bounds Write (CWE-787) 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 23.2th 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).
Deeper analysis
CVE-2026-2793 encompasses multiple memory safety bugs, classified under CWE-787 (Out-of-bounds Write), present in Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147, and Thunderbird 147. These bugs demonstrated evidence of memory corruption in some cases, with Mozilla presuming that sufficient effort could lead to exploitation for arbitrary code execution.
The vulnerability carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), making it remotely exploitable over a network with low complexity, no required privileges or user interaction. Attackers could leverage these flaws to achieve high-impact compromise, including unauthorized access to sensitive data, modification of system integrity, and disruption of availability, potentially through crafted content processed by the affected browsers or email client.
Mozilla's security advisories (MFSA2026-13 through MFSA2026-16) and associated Bugzilla entries (bugs 2015196, 2016423, 2016498) detail the fixes, which were released in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8. Security practitioners should prioritize updating to these patched versions to mitigate the risks.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8445
Vulnerability details
Memory safety bugs present in Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have…
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been exploited to run arbitrary code. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Memory corruption RCE via crafted remote content in browser/email client directly enables drive-by compromise (T1189) and exploitation for client execution (T1203).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires identification, reporting, and correction of system flaws like the memory safety bugs in CVE-2026-2793 through timely patching to updated Firefox and Thunderbird versions.
Implements security safeguards such as address space layout randomization and data execution prevention to protect against exploitation of memory corruption from out-of-bounds writes in affected browsers.
Enables vulnerability scanning to identify and prioritize unpatched instances of vulnerable Firefox ESR, Firefox, and Thunderbird versions exposed to this CVE.