Is CVE-2026-42387 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-42387 being exploited in the wild.

How severe is CVE-2026-42387?

Medium severity, with a CVSS score of 5.9, published 25 June 2026.

Which products and versions are affected?

Powerdns Recursor 5.2.0 to 5.2.10, 5.3.0 to 5.3.7, 5.4.0 to 5.4.2.

Is there a fix for CVE-2026-42387?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-42387 attacked?

It is attacked over the network, in a hosted service.

Am I affected by CVE-2026-42387?

Check whether you run Powerdns Recursor at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-42387: PowerDNS Recursor denial of service in ZoneToCache

CVE-2026-42387 · Severity: medium · CVSS 5.9 · Published 2026-06-25

A vulnerability in the PowerDNS Recursor, a service used to translate human-readable domain names into IP addresses, could allow a malicious server to crash the system. By sending a specially crafted data zone, an attacker can trigger a service failure, leading to a denial of service for users relying on that DNS server. This impact is limited to service availability and does not involve data theft or unauthorized access.

Technologies: Powerdns Recursor. Vendors: Powerdns.

Quick answers

Is CVE-2026-42387 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-42387 being exploited in the wild.
How severe is CVE-2026-42387?: Medium severity, with a CVSS score of 5.9, published 25 June 2026.
Which products and versions are affected?: Powerdns Recursor 5.2.0 to 5.2.10, 5.3.0 to 5.3.7, 5.4.0 to 5.4.2.
Is there a fix for CVE-2026-42387?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-42387 attacked?: It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-42387?: Check whether you run Powerdns Recursor at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A denial of service vulnerability exists in PowerDNS Recursor's ZoneToCache function due to insufficient input validation in the zonemd.cc component. A malicious authoritative server can exploit this by sending a specially crafted zone, causing the Recursor process to crash. The attack requires the Recursor to be configured to fetch and cache zones from the attacker-controlled server. The vulnerability is addressed in versions 5.2.11, 5.3.8, and 5.4.3.

Affected products

PowerDNS Recursor 5.2.0 to 5.2.10, 5.3.0 to 5.3.7, 5.4.0 to 5.4.2

Timeline

2026-06-25: disclosed: Initial advisory publication

References

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