Vulnerability Description
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 Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Nlnetlabs | Unbound | >= 1.16.2, < 1.25.2 |
Related Weaknesses (CWE)
References
FAQ
What is CVE-2026-42955?
CVE-2026-42955 is a vulnerability with a CVSS score of 3.7 (LOW). 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 d...
How severe is CVE-2026-42955?
CVE-2026-42955 has been rated LOW with a CVSS base score of 3.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-42955?
Check the references section above for vendor advisories and patch information. Affected products include: Nlnetlabs Unbound.