What’s Vulnerable › Vulnerabilities

CVE-2025-4093: Memory safety bug fixed in Firefox ESR 128.10 and Thunderbird 128.10

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-04-29 · updated 2026-10-05
• Weakness: CWE-119

Description

Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.10 and Thunderbird 128.10.

Affected products

• Mozilla Firefox: before 128.10 — fixed in 128.10
• Mozilla Thunderbird: before 128.10.0 — fixed in 128.10.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 128.10; Mozilla Thunderbird 128.10.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1894100
• https://www.mozilla.org/security/advisories/mfsa2025-29/
• https://www.mozilla.org/security/advisories/mfsa2025-32/
• https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html

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