CVE-2026-42955

NameCVE-2026-42955
DescriptionIn 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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
unbound (PTS)bullseye1.13.1-1+deb11u2vulnerable
bullseye (security)1.13.1-1+deb11u7vulnerable
bookworm1.17.1-2+deb12u4vulnerable
bookworm (security)1.17.1-2+deb12u3vulnerable
trixie (security), trixie1.22.0-2+deb13u3vulnerable
forky, sid1.26.0-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
unboundsource(unstable)1.25.2-1

Notes

https://community.nlnetlabs.nl/t/unbound-1-25-2-released/3430

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