cyrusimap Cyrus IMAP up to 3.12.2 URLAUTH mboxkey weak password hash

Summaryinfo

A vulnerability described as problematic has been identified in cyrusimap Cyrus IMAP up to 3.12.2. Affected by this issue is some unknown functionality of the component URLAUTH. Such manipulation of the argument mboxkey leads to weak password hash. This vulnerability is uniquely identified as CVE-2026-47085. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in cyrusimap Cyrus IMAP up to 3.12.2. Affected by this issue is an unknown code block of the component URLAUTH. The manipulation of the argument mboxkey with an unknown input leads to a weak password hash vulnerability. Using CWE to declare the problem leads to CWE-916. The product generates a hash for a password, but it uses a scheme that does not provide a sufficient level of computational effort that would make password cracking attacks infeasible or expensive. Impacted is confidentiality. CVE summarizes:

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.)

The advisory is available at cyrusimap.org. This vulnerability is handled as CVE-2026-47085 since 05/18/2026. The exploitation is known to be difficult. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1552 by the MITRE ATT&CK project.

Upgrading to version 3.12.3 eliminates this vulnerability.

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Productinfo

Vendor

• cyrusimap

Name

• Cyrus IMAP

Version

• 3.12.0
• 3.12.1
• 3.12.2

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CPE 2.2info

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