CVE-2026-12327

HIGH 7.3

Memory safety bugs fixed in Firefox ESR 140.12, Thunderbird ESR 140.12, Firefox 152 and Thunderbird 152

CVSS Score

7.3

EPSS Score

0.0%

EPSS Percentile

0th

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 run arbitrary code. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

Vendor	mozilla
Product	firefox
Ecosystems	Browser JavaScript
Industries	Technology
Published	Jun 16, 2026
Last Updated	Jun 16, 2026

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Affected Versions

Mozilla / Firefox

All versions affected

Mozilla / Thunderbird

All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗

bugzilla.mozilla.org: https://bugzilla.mozilla.org/buglist.cgi?bug_id=2011842%2C2023902%2C2025512%2C2027312%2C2029444%2C2036571%2C2036900%2C2036936%2C2037995%2C2038551%2C2040717%2C2042724 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-57/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-58/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-60/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-61/

Credits

Christian Holler, Jens Stutte, Nika Layzell, Randell Jesup, Tom Schuster and the Mozilla Fuzzing Team