CVE-2026-42387 Insufficient input validation in ZoneToCache
A malicious authoritative server can crash the PowerDNS Recursor by sending a crafted zone due to insufficient input validation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42387?
CVE-2026-42387 is a medium-severity denial of service vulnerability in PowerDNS Recursor, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A malicious authoritative server can send a crafted zone via the ZoneToCache function that leads to a crash of the Recursor due to insuffcient input validation.
Weakness: CWE-20
Which versions are affected by CVE-2026-42387?
How do I fix CVE-2026-42387?
Apply the vendor's patch.
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-2026-42387 being exploited?
There is no known exploitation of CVE-2026-42387 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-42387, GHSA-9v36-5rhx-cq6m, UBUNTU-CVE-2026-42387.