CVE-2026-61911 [MEDIUM] – An issue was discovered in Cyrus IMAP before 3.12.4. There is a Sieve mailbox existence or

An issue was discovered in Cyrus IMAP before 3.12.4. There is a Sieve mailbox existence oracle. An authenticated user could install a Sieve script that probed whether another user’s private mailbox existed, or read the value of shared mailbox annotations, by observing which fileinto branch fired during LMTP delivery.