What’s Vulnerable › Vulnerabilities

CVE-2025-9181: Uninitialized memory in the JavaScript Engine component

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-08-19 · updated 2026-10-05
• Weakness: CWE-457

Description

Uninitialized memory in the JavaScript Engine component. This vulnerability was fixed in Firefox 142, Firefox ESR 128.14, Firefox ESR 140.2, Thunderbird 142, Thunderbird 128.14, and Thunderbird 140.2.

Affected products

• Mozilla Firefox: before 128.14.0; before 142.0; from 140.0 before 140.2.0 — fixed in 128.14.0, 140.2.0, 142.0
• Mozilla Thunderbird: before 128.14.0; before 142.0; from 140.0 before 140.2.0 — fixed in 128.14.0, 140.2.0, 142.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 128.14.0, 140.2.0, 142.0; Mozilla Thunderbird 128.14.0, 140.2.0, 142.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1977130
• https://www.mozilla.org/security/advisories/mfsa2025-64/
• https://www.mozilla.org/security/advisories/mfsa2025-66/
• https://www.mozilla.org/security/advisories/mfsa2025-67/
• https://www.mozilla.org/security/advisories/mfsa2025-70/
• https://www.mozilla.org/security/advisories/mfsa2025-71/
• https://www.mozilla.org/security/advisories/mfsa2025-72/
• https://lists.debian.org/debian-lts-announce/2025/08/msg00016.html
• https://lists.debian.org/debian-lts-announce/2025/08/msg00018.html

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