CVE-2026-33604: open-xchange gmbh ox dovecot ce Insufficient Psychological Acceptability

Vulnerability summary

CVE-2026-33604 is a medium (CVSS 5.9) Insufficient Psychological Acceptability vulnerability in open-xchange gmbh ox dovecot ce. EPSS estimates a 0.31% chance of exploitation in the next 30 days, higher than 22.9% of scored vulnerabilities.

Timeline

1. 28-08-2026
   PublishedVulnerability first disclosed.
2. 28-08-2026
   Last modifiedVulnerability information updated.

Description

An attacker that can get Dovecot to relay a message, for example through Sieve redirect or submission relay, can use a crafted line ending in the message body to bypass the outbound protection that prevents message content from being interpreted as SMTP commands. A downstream mail server that hasn't yet fixed the SMTP smuggling vulnerability can be tricked into treating part of the message body as new SMTP commands, allowing injection of spoofed email. This is the same vulnerability class as CVE-2023-51764 and CVE-2023-51766. Where you control the receiving mail servers, ensure they reject bare carriage returns in message data. Update to non-vulnerable version. No publicly available exploits are known.

• CWE-655Insufficient Psychological AcceptabilityThe product has a protection mechanism that is too difficult or inconvenient to use, encouraging non-malicious users to disable or bypass the mechanism, whether by accident or on purpose.