CVE-2026-92240 – A malicious or compromised IMAP server can trigger an out-of-bounds read in the IMAP respo

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 and Thunderbird 140.16.