CVE-2026-46582
LowCVSS 3.7Exploitation Probability (EPSS)
Low risk9th percentile - higher than 9% of all known CVEs
Summary
In NLnet Labs Unbound from 1.6.0 to 1.25.1, a wildcard RRset replay can be temporarily considered DNSSEC-secure based on RRSIG validation and cached. Later NSEC validation marks it as bogus, but another thread may use it for a reply, replacing a specific record with a wildcard. The attack requires a DNSSEC-signed domain and a CNAME record pointing to a sibling record of a wildcard.
Risk Assessment
A malicious actor can poison the Unbound cache, replacing records with wildcards, leading to false DNS responses and potential traffic redirection.
Recommendation
Update Unbound to a patched version and enable full NSEC validation before using cached responses.
Original NVD description (English source)
In NLnet Labs Unbound 1.6.0 up to and including 1.25.1, a replay of a wildcard rrset as another piece of data, could be briefly considered DNSSEC secure based only on the RRSIG validation and stored into cache, before later validation treats it as bogus based on NSEC validation. When the resolving thread puts secure on the rrset, and another thread that is on the serve expired path then picks up the updated rrset contents with the secure status for a reply, it can be used to change a specific record, next to a wildcard that could be covered by the wildcard, into the wildcard. A malicious actor can exploit the possible poisonous effect by having any DNSSEC-singed domain (irrelevant to the victim domain) and a CNAME wrapper record that points to a record next to a wildcard (that could be covered by the wildcard). Then quering Unbound for the wildcard sibling record would seed the secure message. A later (after expiry) query for the CNAME wrapper would need to resolve the target sibling record. If the wildcard replay is injected into the response, the wildcard rrset will update the expired sibling record with a secure status before completing proper wildcard validation with NSEC records and eventually treating the CNAME wrapper answer as bogus. The updated poisoned rrset is now secure and points to the wildcard. This vulnerability is explicit for the serve expired path and needs injection of the signed wildcard rrset without the NSEC accompanying rrset.