CVE-2026-92239: Buffer overrun in IMAP

Severity: high (CVSS 8.1 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: 2026-09-15 · updated 2026-09-24
Weakness: CWE-125

Description

A maliciously constructed IMAP line could cause an out-of-bounds buffer read. This vulnerability was fixed in Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.

Affected products

Mozilla Thunderbird: before 140.16.0; from 141.0 before 153.3.0; from 154.0 before 156.0 — fixed in 140.16.0, 153.3.0, 156.0

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 140.16.0, 153.3.0, 156.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2060488
https://www.mozilla.org/security/advisories/mfsa2026-94/
https://www.mozilla.org/security/advisories/mfsa2026-95/
https://www.mozilla.org/security/advisories/mfsa2026-96/

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