CVE-2026-2781: Integer overflow in the Libraries component in NSS

Severity: critical (CVSS 9.8 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: 2026-02-24 · updated 2026-06-17
Weakness: CWE-190

Description

Integer overflow in the Libraries component in NSS. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, Thunderbird 140.8, and Firefox ESR 115.35.

Affected products

Mozilla Firefox: before 140.8.0; before 148.0 — fixed in 140.8.0, 148.0
Mozilla Thunderbird: before 140.8.0; before 148.0 — fixed in 140.8.0, 148.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 140.8.0, 148.0; Mozilla Thunderbird 140.8.0, 148.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2009552
https://www.mozilla.org/security/advisories/mfsa2026-13/
https://www.mozilla.org/security/advisories/mfsa2026-15/
https://www.mozilla.org/security/advisories/mfsa2026-16/
https://www.mozilla.org/security/advisories/mfsa2026-17/
https://www.mozilla.org/security/advisories/mfsa2026-31/
https://lists.debian.org/debian-lts-announce/2026/03/msg00012.html

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