CVE-2025-1020

CRITICAL 9.8

Memory safety bugs fixed in Firefox 135 and Thunderbird 135

CVSS Score

9.8

EPSS Score

0.0%

EPSS Percentile

0th

Memory safety bugs present in Firefox 134 and Thunderbird 134. 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 135 and Thunderbird 135.

Vendor	mozilla
Product	firefox
Ecosystems	Browser JavaScript
Industries	Technology
Published	Feb 4, 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=1939063%2C1942169 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-07/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-11/

Credits

The Mozilla Fuzzing Team