CVE-2026-44690: nlnet labs unbound

Vulnerability summary

CVE-2026-44690 is a high (CVSS 7.5) vulnerability in nlnet labs unbound. EPSS estimates a 0.15% chance of exploitation in the next 30 days, higher than 4% of scored vulnerabilities.

Timeline

1. 22-07-2026
   PublishedVulnerability first disclosed.
2. 22-07-2026
   Last modifiedVulnerability information updated.

Description

In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, insufficient validation of the RRSIG.Labels field combined with premature cache writes during RFC 8198 aggressive NSEC processing leads to cache poisoning that permits a malicious actor controlling a single delegated zone to poison arbitrary sibling zones under NSEC-signed parent domains. A malicious actor with one registered domain under an NSEC-signed TLD can serve malicious insecure DNS responses for unrelated sibling domains (sharing the same parent zone). Arbitrary delegations that do not exist under the parent domain and are covered by the parent's NSEC chain can be brought into insecure existence by fraudulent wildcard DS records (less labels than expected, unknown algorithm) from the malicious sibling domain. This allows the malicious actor to inject insecure wildcard records for those delegations.

• CWE-345Insufficient Verification of Data AuthenticityThe product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.