CVE-2026-33263

NameCVE-2026-33263
DescriptionWhen mail_max_userip_connections is set (default 10) and reached, submission-login can crash with epoll() panic caused by file descriptor handling issues. If running in high-security mode (default for community releases), only the new submission connection gets terminated. If running in high-performance mode (default for Pro releases), all connections handled by the submission-login process will be terminated. The crashes can cause failure for user to send a message, or it can cause duplicate messages to be sent. If TLS is not used (in the backend server processing the submission), duplicate deliveries cannot happen, because the crash can only happen at AUTH stage. Limit the number of connections handled by single submission-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs1146018

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
dovecot (PTS)bookworm, bookworm (security)1:2.3.19.1+dfsg1-2.1+deb12u6vulnerable
trixie (security), trixie1:2.4.1+dfsg1-6+deb13u6vulnerable
forky, sid1:2.4.5+dfsg1-2fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
dovecotsource(unstable)1:2.4.5+dfsg1-11146018

Notes

https://documentation.open-xchange.com/dovecot/security/advisories/html/2026/oxdc-adv-2026-0003.html#cve-2026-33263-submission-login-panic-when-mail-max-userip-connections-is-reached-panic-epoll-ctl-del-8-failed-bad-file-descriptor

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