CVE-2026-33604 Other in OX Dovecot CE
Attackers can bypass SMTP smuggling protections in Dovecot to inject spoofed emails into downstream servers via crafted message body line endings.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33604?
CVE-2026-33604 is a medium-severity vulnerability in Open-Xchange GmbH OX Dovecot CE, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-655
Which versions are affected by CVE-2026-33604?
How do I fix CVE-2026-33604?
Upgrade to a fixed version.
Is CVE-2026-33604 being exploited?
There is no known exploitation of CVE-2026-33604 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-33604, AZL-98280, DEBIAN-CVE-2026-33604, GHSA-ccxf-782r-4742, UBUNTU-CVE-2026-33604.