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Vulnerability · Published Oct 21, 2026 · Assigned by NLnet Labs

CVE-2026-50106Possible insecure NXDOMAIN for non-existing records under a configured island trust anchor underneath an insecure parent.

Medium 6.5

In plain English

A medium-severity security flaw in Unbound from NLnet Labs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 11% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.2%top 89.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12unboundno fix listedDEBIAN-CVE-2026-50106
Debian:13unbound1.26.2-0+deb13u1DEBIAN-CVE-2026-50106
Debian:14unbound1.26.2-1DEBIAN-CVE-2026-50106
Ubuntu:22.04:LTSunboundno fix listedUBUNTU-CVE-2026-50106
Ubuntu:24.04:LTSunboundno fix listedUBUNTU-CVE-2026-50106
Ubuntu:26.04:LTSunboundno fix listedUBUNTU-CVE-2026-50106
Ubuntu:26.10unboundno fix listedUBUNTU-CVE-2026-50106

Affected products (as reported)

VendorProductVersions
NLnet Labs Unbound 0 – before 1.26.2

Weakness: CWE-807 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

References