CVE-2026-50106

Medium

Description

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.

SeverityMedium
CVSS6.5
Exploit probability—
ProductUnbound
PublishedOct 21, 2026
First seenOct 21, 2026
Weakness typeCWE-807CWE-807

How to fix

Update
  • NLnet Labs Unbound1.26.2 or later

Affected products

ProductAffected versionsFixed in
NLnet Labs Unboundv < 1.26.21.26.2

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