Vulnerability in Nlnet Labs Unbound
CVE-2026-50106
When NLnet Labs Unbound up to and including version 1.26.1 is configured with both a root trust anchor and an additional 'trust-anchor:' for an island-of-security zone whose parent is provably insecure under the root chain, a malicious actor who can deliver one forged NXDOMAIN response for a name inside the island, with the NSEC/SOA RRSIG 'SignerName' set to the insecure parent, tricks Unbound's validator to use the root trust anchor instead, and consecutively the insecure parent, thus causing that record to be treated as insecure and denying existence for records in the trust island.
Published .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- www.nlnetlabs.nl/downloads/unbound/CVE-2026-50106.txt (vendor-advisory)
Frequently asked questions
- What is CVE-2026-50106?
- CVE-2026-50106 is a medium-severity vulnerability in Nlnet Labs Unbound, classified under CWE-807. CVSS score: 6.5/10. Published 2026-10-21.
- How severe is CVE-2026-50106?
- Medium severity. CVSS v3 base score is 6.5 out of 10.