CVE-2026-42955
LowCVSS 3.7Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
Unbound DNS server versions 1.16.2 through 1.25.1 are vulnerable to a 'ghost domain names' attack, allowing an adversary controlling a ghost zone to extend the ghost domain window by one configured TTL for A/AAAA glue records. With 'harden-referral-path: yes', no client query is needed.
Risk Assessment
An attacker can keep fake DNS records cached longer than intended, enabling traffic redirection or man-in-the-middle attacks on ghost domains.
Recommendation
Update Unbound to a version above 1.25.1 or apply the available patch. Consider setting 'harden-referral-path: no' to reduce risk.
Original NVD description (English source)
In NLnet Labs Unbound 1.16.2 up to and including 1.25.1, a similar vulnerability as with CVE-2026-40622 in the 'ghost domain names' family of attacks was found in Unbound that could extend the ghost domain window by up to one cached TTL configured value for A/AAAA glue records. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client A/AAAA query can cause Unbound to overwrite the cached expired parent-side glue rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client query is required since Unbound implicitly performs that query. This is a variant of CVE-2026-40622 which only addressed the NS query.