Bug 2535055 (CVE-2026-80225)

Summary: CVE-2026-80225 unbound: Unbound: Denial of Service via continuous queries on TCP/DoT connection
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Unbound. A malicious actor can exploit a vulnerability in the TCP/DoT reading procedure, which lacks a limit on consecutive reads. By continuously streaming distinct uncached names over a TCP/DoT connection, an attacker can monopolize a worker's event loop. This can lead to a degradation of service, effectively causing a Denial of Service (DoS) for legitimate users.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 2537323    
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Description OSIDB Bzimport 2026-09-16 09:04:51 UTC 
In NLnetLabs Unbound up to and including 1.26.0, a degradation of service vulnerability is present in the TCP/DoT reading procedure where there is no limit on consecutive reads. A malicious actor that can stream and sustain a rate of distinct uncached names over the TCP/DoT connection, monopolizes a single worker's entire event loop for as long as its writes stay ahead of the drain.