CVE-2026-42395 Denial of service in OX Dovecot CE
A trusted proxy sending a NUL byte in forwarding info crashes the login process, causing denial of service for mail logins.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42395?
CVE-2026-42395 is a medium-severity denial of service vulnerability in Open-Xchange GmbH OX Dovecot CE, published on 28 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A host listed as a trusted proxy can send forwarding information containing a NUL byte, which crashes the login process on the following login attempt. The login process is terminated, which can cause degradation or denial of service for logins. Deployments that do not configure trusted proxies are not affected. Restrict the list of trusted proxy networks to hosts that are fully under your control. Update to non-vulnerable version. No publicly available exploits are known.
Weakness: CWE-400
Which versions are affected by CVE-2026-42395?
How do I fix CVE-2026-42395?
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-2026-42395 being exploited?
There is no known exploitation of CVE-2026-42395 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-42395, AZL-98265, DEBIAN-CVE-2026-42395, GHSA-gvmq-26g6-c3qh, UBUNTU-CVE-2026-42395.