What’s Vulnerable › Vulnerabilities

CVE-2025-1012: Use-after-free during concurrent delazification

• Severity: high (CVSS 7.5 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: 2025-02-04 · updated 2026-10-05
• Weakness: CWE-416

Description

A race during concurrent delazification could have led to a use-after-free. This vulnerability was fixed in Firefox 135, Firefox ESR 115.20, Firefox ESR 128.7, Thunderbird 128.7, and Thunderbird 135.

Affected products

• Mozilla Firefox: before 115.20.0; before 135.0; from 128.1.0 before 128.7.0 — fixed in 115.20.0, 128.7.0, 135.0
• Mozilla Thunderbird: before 135.0; from 128.0.1 before 128.7.0 — fixed in 128.7.0, 135.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 115.20.0, 128.7.0, 135.0; Mozilla Thunderbird 128.7.0, 135.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1939710
• https://www.mozilla.org/security/advisories/mfsa2025-07/
• https://www.mozilla.org/security/advisories/mfsa2025-08/
• 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/msg00005.html
• https://lists.debian.org/debian-lts-announce/2025/02/msg00006.html

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