CVE-2026-27852 Denial of service in OX Dovecot CE
An attacker can cause a denial of service by sending crafted emails that exhaust memory during IMAP parsing, affecting Dovecot users.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-27852?
CVE-2026-27852 is a high-severity denial of service vulnerability in Open-Xchange GmbH OX Dovecot CE, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
An attacker that can send mail to a user can craft a message whose headers contain a very large number of email addresses or MIME parameters, which causes excessive memory usage when the message is later parsed. The message is still delivered, but reading it over IMAP can exhaust the memory limit of the process and terminate it, causing denial of service for the affected user. Update to non-vulnerable version. No publicly available exploits are known.
Weakness: CWE-400
Which versions are affected by CVE-2026-27852?
How do I fix CVE-2026-27852?
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-2026-27852 being exploited?
There is no known exploitation of CVE-2026-27852 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-27852, AZL-98289, DEBIAN-CVE-2026-27852, GHSA-8fwp-48xw-q2gf, UBUNTU-CVE-2026-27852.