CVE-2026-33604
Received
Received - Intake
Dovecot SMTP Smuggling via Message Body Crafted Line Endings
Vulnerability report for CVE-2026-33604, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-08-28
Last updated on: 2026-08-28
Assigner: Open-Xchange
Description
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 Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| dovecot | dovecot | * |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-655 | The 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. |
