What’s Vulnerable › Vulnerabilities

CVE-2026-92240: Out-of-bounds read in IMAP response parser

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% 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 malicious or compromised IMAP server can trigger an out-of-bounds read in the IMAP response parser by sending an untagged '* ID' response, crashing Thunderbird. The affected parsing path is reachable before authentication. 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=2069113
• 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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