Bug 2476465 (CVE-2026-40020)

Summary: CVE-2026-40020 dovecot: dovecot: Denial of Service via IMAP SETACL command injection
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in dovecot. A remote attacker can exploit the Internet Message Access Protocol (IMAP) SETACL command to inject "anyone" permissions into a user's dovecot-acl file, even when the imap_acl_allow_anyone setting is disabled. This vulnerability allows an attacker to spam folders to all users, leading to a denial of service by disrupting normal email service. No unauthorized access to user data is gained.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2479587, 2479589, 2479588    
Bug Blocks:    

Description OSIDB Bzimport 2026-05-12 14:01:32 UTC
Attacker can use the IMAP SETACL command to inject the anyone permission to user's dovecot-acl file even if imap_acl_allow_anyone=no. This causes folders to be spammed to all users. The impact is limited to being able to spam folders to other users, no unexpected access is gained. Install to fixed version. No publicly available exploits are known.