What is CVE-2026-42959?

CVE-2026-42959 is a high-severity vulnerability in Nlnet Labs Unbound, classified under Access of Uninitialized Pointer. CVSS score: 7.5/10. Published 2026-05-20.

How severe is CVE-2026-42959?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Nlnet Labs Unbound

CVE-2026-42959

NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the…

EPSS: 0.001 (18.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Nlnet Labs Unbound — versions 0
Nlnetlabs Unbound

Weakness classification (CWE)

CWE-824 — Access of Uninitialized Pointer

References

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

Frequently asked questions

What is CVE-2026-42959?: CVE-2026-42959 is a high-severity vulnerability in Nlnet Labs Unbound, classified under Access of Uninitialized Pointer. CVSS score: 7.5/10. Published 2026-05-20.
How severe is CVE-2026-42959?: High severity. CVSS v3 base score is 7.5 out of 10.