Bug 2525545 (CVE-2026-42391)

Summary: CVE-2026-42391 dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in Dovecot. An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in. This action causes the server to consume excessive memory and CPU resources, leading to the termination of login processes and other active connections. This can result in a degradation or complete denial of service for IMAP logins.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 2526685    
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Description OSIDB Bzimport 2026-08-28 11:22:04 UTC 
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.