Threat Intelligence Database

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.

NLnet Labs Unbound versions 1.6.2 through 1.25.0 have a denial of service vulnerability when compiled with DNSCrypt support. A specially crafted DNSCrypt query with decrypted plaintext of all zero bytes and missing an expected marker can cause Unbound to read beyond the intended buffer, potentially causing a heap overflow and crash. The likelihood of a crash is low and depends on the memory allocator and layout. Version 1.25.1 includes a patch that bounds the reading to prevent this issue.