CVE-2026-40015 Denial of service in OX Dovecot CE
Authenticated attackers can crash the IMAP hibernation service via invalid commands, causing service degradation for hibernated sessions.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40015?
CVE-2026-40015 is a medium-severity denial of service vulnerability in Open-Xchange GmbH OX Dovecot CE, published on 28 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
An attacker that has valid credentials can open many connections to the imap-hibernate service and send invalid commands, which can intermittently cause an out-of-bounds read and crash the process. The crash interrupts hibernated IMAP sessions handled by the affected process, which can cause degradation of service for IMAP. Disable IMAP hibernation. Update to non-vulnerable version. No publicly available exploits are known.
Weakness: CWE-125
Which versions are affected by CVE-2026-40015?
How do I fix CVE-2026-40015?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-40015 being exploited?
There is no known exploitation of CVE-2026-40015 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-40015, AZL-98328, DEBIAN-CVE-2026-40015, GHSA-qx86-c9pp-83v2, UBUNTU-CVE-2026-40015.