What’s Vulnerable › Vulnerabilities

CVE-2025-1017: Memory safety bugs fixed in Firefox 135, Thunderbird 135, Firefox ESR 128.7, and Thunderbird 128.7

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-02-04 · updated 2026-10-05
• Weakness: CWE-787

Description

Memory safety bugs present in Firefox 134, Thunderbird 134, Firefox ESR 128.6, and Thunderbird 128.6. 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, Firefox ESR 128.7, Thunderbird 128.7, and Thunderbird 135.

Affected products

• Mozilla Firefox: before 128.7.0; before 135.0 — fixed in 128.7.0, 135.0
• Mozilla Thunderbird: from 128.0.1 before 128.7.0; from 131.0 before 135.0 — fixed in 128.7.0, 135.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 128.7.0, 135.0; Mozilla Thunderbird 128.7.0, 135.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/buglist.cgi?bug_id=1926256%2C1935984%2C1935471
• https://www.mozilla.org/security/advisories/mfsa2025-07/
• https://www.mozilla.org/security/advisories/mfsa2025-09/
• https://www.mozilla.org/security/advisories/mfsa2025-10/
• https://www.mozilla.org/security/advisories/mfsa2025-11/
• https://lists.debian.org/debian-lts-announce/2025/02/msg00006.html

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