CVE-2026-42955: low-severity vulnerability in NLnet Labs Unbound
Extra fix for CVE-2026-40622 to also clamp the TTL of A/AAAA records disallowing a one-time 'ghost domain' delegation renewal via glue records
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
8Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 3.7epss 0.2%
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.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Affected products
NLnet Labs · UnboundRelated CVEs — NLnet Labs Unbound
In the same product, most dangerous first.
CVE-2024-1931HIGHDenial of service when trimming EDE text on positive repliesEPSS 2.5%CVE-2022-3204HIGHNRDelegation AttackEPSS 1.6%CVE-2026-33278CRITICALPossible arbitrary code execution during DNSSEC validationEPSS 1.4%CVE-2022-30699—Novel "ghost domain names" attack by updating almost expired delegation informationEPSS 1.2%CVE-2022-30698—Novel "ghost domain names" attack by introducing subdomain delegationsEPSS 1.2%CVE-2026-81642CRITICALHeap buffer overflow and possible Remote Code Execution when digesting DNSKEYEPSS 1.0%