CVE-2026-40622 (GCVE-0-2026-40622)
Vulnerability from cvelistv5 – Published: 2026-05-20 09:18 – Updated: 2026-05-20 12:12
VLAI
EPSS
VEX
Title
Another 'ghost domain names' attack variant
Summary
NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. 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 NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS 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 NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.
Severity
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-20 12:12 UTC
CWE
- CWE-346 - Origin Validation Error
Assigner
NLnet Labs
CNA
References
1 reference
| URL | Tags |
|---|---|
| https://www.nlnetlabs.nl/downloads/unbound/CVE-20… | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| NLnet Labs | Unbound |
Affected:
1.16.2 , < 1.25.1
(semver)
|
Date Public
2026-05-20 00:00
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