CVE-2026-12327
Published: 16 June 2026
Summary
CVE-2026-12327 is a high-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Mozilla Firefox. Its CVSS base score is 8.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 32.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-37073
Vulnerability details
Memory safety bugs present in Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151 and Thunderbird 151. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to…
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run arbitrary code. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Memory corruption in client application (browser) directly enables exploitation for arbitrary code execution on the client.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Ongoing control assessments and code testing (static/dynamic analysis, fuzzing) surface memory buffer restriction failures, which are then remediated before release.
Managed runtimes used by platform-independent applications (e.g., JVM, CLR) enforce memory safety, preventing most buffer overflows that require direct memory manipulation.
Memory protections (e.g., W^X, ASLR) make exploitation of buffer-boundary violations far harder to turn into code execution.
Detects exploitation attempts that produce memory corruption, crashes, or anomalous behavior.