1. Home
  2. CVE Database
  3. CVE-2026-33604
MEDIUM · 5.9

CVE-2026-33604

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 pr...

Vulnerability 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.

CVSS Score

5.9

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE

Related Weaknesses (CWE)

CWE-655

References

FAQ

What is CVE-2026-33604?

CVE-2026-33604 is a vulnerability with a CVSS score of 5.9 (MEDIUM). 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 pr...

How severe is CVE-2026-33604?

CVE-2026-33604 has been rated MEDIUM with a CVSS base score of 5.9/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-33604?

Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.