What is CVE-2026-50251?

CVE-2026-50251 is a medium-severity vulnerability in Nlnet Labs Unbound, classified under Incomplete List of Disallowed Inputs. CVSS score: 5.3/10. Published 2026-07-22.

How severe is CVE-2026-50251?

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

Vulnerability in Nlnet Labs Unbound

CVE-2026-50251

In NLnet Labs Unbound up to and including version 1.25.1, when 'unwanted-reply-threshold' is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by i…

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

Weakness classification (CWE)

CWE-184 — Incomplete List of Disallowed Inputs

References

sep@nlnetlabs.nl (vendor-advisory)

Frequently asked questions

What is CVE-2026-50251?: CVE-2026-50251 is a medium-severity vulnerability in Nlnet Labs Unbound, classified under Incomplete List of Disallowed Inputs. CVSS score: 5.3/10. Published 2026-07-22.
How severe is CVE-2026-50251?: Medium severity. CVSS v3 base score is 5.3 out of 10.