Vulnerability in Open-Xchange Gmbh Ox Dovecot Pro
CVE-2026-33263
When 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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.006 (44.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 45th percentile — 44.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.006 · change: +0.003
Affected products
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-33263?
- CVE-2026-33263 is a medium-severity vulnerability in Open-Xchange Gmbh Ox Dovecot Pro, classified under Exposure of File Descriptor to Unintended Control Sphere (File Descriptor Leak). CVSS score: 4.3/10. Published 2026-08-28.
- How severe is CVE-2026-33263?
- Medium severity. CVSS v3 base score is 4.3 out of 10.