CVE-2025-1020

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 affects Firefox < 135 and Thunderbird < 135.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTNIST
9.8 CRITICAL
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
mozillaCNA
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CISA-ADPADP
9.8 CRITICAL
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 34%
VendorProductVersion
mozillafirefox
𝑥
< 135.0
mozillathunderbird
131.0 ≤
𝑥
< 135.0
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
firefox
sid
139.0-1
fixed
Common Weakness Enumeration
References
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1939063%2C1942169
https://www.mozilla.org/security/advisories/mfsa2025-07/
https://www.mozilla.org/security/advisories/mfsa2025-11/