Bug 2525537 (CVE-2026-33604)

Summary: CVE-2026-33604 dovecot: Dovecot: SMTP smuggling vulnerability allows spoofed email injection
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Dovecot. A remote attacker can exploit this by crafting a message with a specific line ending. If Dovecot relays this message, it can bypass security protections, allowing the attacker to inject spoofed email into a vulnerable downstream mail server. This vulnerability is related to SMTP (Simple Mail Transfer Protocol) smuggling.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2526668    
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Description OSIDB Bzimport 2026-08-28 11:21:40 UTC 
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.