🔐 CVE Alert

CVE-2025-6436

HIGH 8.1

Memory safety bugs fixed in Firefox 140 and Thunderbird 140

CVSS Score
8.1
EPSS Score
0.0%
EPSS Percentile
0th

Memory safety bugs present in Firefox 139 and Thunderbird 139. 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 140 and Thunderbird 140.

Vendor mozilla
Product firefox
Ecosystems
Industries
Technology
Published Jun 24, 2025
Last Updated Apr 13, 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=1941377%2C1960948%2C1966187%2C1966505%2C1970764%2C1942930 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-51/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-54/

Credits

Andrew McCreight, Gabriele Svelto, Beth Rennie (she/her), Steven Michaud, the Mozilla Fuzzing Team