Bug 2506144 (CVE-2026-42955)

Summary: CVE-2026-42955 unbound: Unbound: DNS cache integrity issue
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Priority: low    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A "ghost domain names" flaw in Unbound allows a remote attacker controlling a domain to manipulate cached DNS records. By extending the lifetime of outdated DNS information, an attacker can cause clients to receive stale or misleading DNS responses.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2508066    
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Description OSIDB Bzimport 2026-07-22 14:02:31 UTC 
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.