Bug 2501446 (CVE-2026-47085)

Summary: CVE-2026-47085 cyrus-imapd: Cyrus IMAP: Information disclosure via URLAUTH token forgery
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
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Hardware: All   
OS: Linux   
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A flaw was found in Cyrus IMAP (cyrus-imapd). A remote attacker could exploit a vulnerability related to URLAUTH token forgery, caused by a missing mailbox key. This could allow the attacker to gain unauthorized read access to a victim's mailbox. The likelihood of exploitation is low due to the obscurity of the URLAUTH feature.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2501666    
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Description OSIDB Bzimport 2026-07-16 19:01:21 UTC 
An issue was discovered in cyrus-imapd in Cyrus IMAP through 3.12.2. URLAUTH token forgery can occur via a missing mboxkey. If an attacker knew a folder name on the victim's account for which the victim had never issued an auth URL, they could forge a working URLAUTH token by computing an HMAC-SHA1 value with a predictable key, giving them read access to the mailbox. (URLAUTH is an obscure feature, meaning that the odds of any user actually being susceptible to this attack are very low. Perhaps no public clients use URLAUTH.)