Unbound Vulnerability in NLnet Labs With Root Trust Anchor Misconfiguration
CVE-2026-50106

6.5MEDIUM

Key Information:

Vendor

Nlnet Labs

Status
Unbound
Vendor
CVE Published:
21 October 2026

What is CVE-2026-50106?

A misconfiguration in NLnet Labs' Unbound DNS resolver versions up to and including 1.26.1 can lead to security issues when both a root trust anchor and an additional trust anchor for an insecure zone are configured. In this scenario, a malicious actor may exploit the system by delivering a forged NXDOMAIN response for a domain within the insecure zone. This manipulation tricks Unbound's validation mechanism into incorrectly utilizing the root trust anchor, leading to the assumption that the insecure parent is valid. Consequently, this results in the denial of existence for records in the secured zone, thereby compromising the integrity of the DNS resolution process.

Affected Version(s)

Unbound 0 < 1.26.2

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50106...
vendor-advisory

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Qifan Zhang (Palo Alto Networks)
.