CVE-2026-47085 Auth bypass in Cyrus IMAP
Attackers can forge URLAUTH tokens to read mailbox data if the obscure URLAUTH feature is enabled and folder names are known.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47085?
CVE-2026-47085 is a medium-severity authentication bypass vulnerability in cyrusimap Cyrus IMAP, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.)
Weakness: CWE-340
Which versions are affected by CVE-2026-47085?
How do I fix CVE-2026-47085?
Apply the vendor's patch.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-47085 being exploited?
There is no known exploitation of CVE-2026-47085 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-47085, GHSA-8jrh-wq6h-53c4, UBUNTU-CVE-2026-47085.