CVE-2026-52687 Denial of service in OX Dovecot CE
Authenticated attackers can cause denial of service in IMAP servers by opening multiple connections with high-memory compression algorithms.
- 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-2026-52687?
CVE-2026-52687 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 select a compression algorithm for the IMAP connection whose decompression state requires a large amount of memory, and open several such connections. The memory limit of the process is reached with only a few connections, terminating the process and all connections it handles, which can cause degradation or denial of service for IMAP. Disable IMAP compression. Alternatively limit the number of connections handled by a single imap-login process, though this has a performance impact. Update to non-vulnerable version. No publicly available exploits are known.
Weakness: CWE-400
Which versions are affected by CVE-2026-52687?
How do I fix CVE-2026-52687?
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-2026-52687 being exploited?
There is no known exploitation of CVE-2026-52687 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-52687, AZL-98292, DEBIAN-CVE-2026-52687, GHSA-f7hp-q869-25g3, UBUNTU-CVE-2026-52687.