Vulnerability Details CVE-2026-42955
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 10.5%
CVSS Severity
CVSS v3 Score 3.7
Products affected by CVE-2026-42955
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cpe:2.3:a:nlnetlabs:unbound:1.16.2
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cpe:2.3:a:nlnetlabs:unbound:1.16.3
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cpe:2.3:a:nlnetlabs:unbound:1.17.0
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cpe:2.3:a:nlnetlabs:unbound:1.17.1
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cpe:2.3:a:nlnetlabs:unbound:1.18.0
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cpe:2.3:a:nlnetlabs:unbound:1.19.0
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cpe:2.3:a:nlnetlabs:unbound:1.19.1
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cpe:2.3:a:nlnetlabs:unbound:1.19.2
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cpe:2.3:a:nlnetlabs:unbound:1.19.3
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cpe:2.3:a:nlnetlabs:unbound:1.20.0
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cpe:2.3:a:nlnetlabs:unbound:1.21.0
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cpe:2.3:a:nlnetlabs:unbound:1.21.1
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cpe:2.3:a:nlnetlabs:unbound:1.22.0
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cpe:2.3:a:nlnetlabs:unbound:1.23.0
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cpe:2.3:a:nlnetlabs:unbound:1.23.1
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cpe:2.3:a:nlnetlabs:unbound:1.24.0
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cpe:2.3:a:nlnetlabs:unbound:1.24.1
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cpe:2.3:a:nlnetlabs:unbound:1.24.2
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cpe:2.3:a:nlnetlabs:unbound:1.25.0
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cpe:2.3:a:nlnetlabs:unbound:1.25.1