CVE-2025-59028 Denial of service in OX Dovecot Pro
Attackers can cause denial of service by sending invalid base64 SASL data, disrupting concurrent authentication sessions on Dovecot servers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-59028?
CVE-2025-59028 is a medium-severity denial of service vulnerability in Dovecot Dovecot, published on 27 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all active authentication sessions to fail. Invalid BASE64 data can be used to DoS a vulnerable server to break concurrent logins. Install fixed version or disable concurrency in login processes (heavy perfomance penalty on large deployments). No publicly available exploits are known.
Weakness: CWE-20
Which versions are affected by CVE-2025-59028?
It affects 2 products.
Products include Dovecot Dovecot, Open-Xchange Dovecot.
How do I fix CVE-2025-59028?
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-2025-59028 being exploited?
There is no known exploitation of CVE-2025-59028 in the wild and no public exploit code.
Other vulnerabilities in Dovecot Dovecot
Sources
Also known as ALPINE-CVE-2025-59028, AZL-81686, DEBIAN-CVE-2025-59028, GHSA-9q9x-wwfr-fxqm, UBUNTU-CVE-2025-59028.