What is CVE-2026-42534?

CVE-2026-42534 is a medium-severity vulnerability in Nlnet Labs Unbound, classified under Expected Behavior Violation. CVSS score: 5.3/10. Published 2026-05-20.

How severe is CVE-2026-42534?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Nlnet Labs Unbound

CVE-2026-42534

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and n…

EPSS: 0.000 (14.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

Affected products

Nlnet Labs Unbound — versions 0
Nlnetlabs Unbound

Weakness classification (CWE)

CWE-440 — Expected Behavior Violation

References

sep@nlnetlabs.nl (vendor-advisory, Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-42534?: CVE-2026-42534 is a medium-severity vulnerability in Nlnet Labs Unbound, classified under Expected Behavior Violation. CVSS score: 5.3/10. Published 2026-05-20.
How severe is CVE-2026-42534?: Medium severity. CVSS v3 base score is 5.3 out of 10.