Bug 2568760 (CVE-2026-123596)

Summary: CVE-2026-123596 hickory-proto: hickory-net: Hickory DNS: Denial of Service via improper DNSSEC NSEC record validation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: dbosanac, jcantril, jlanda, jreimann, kshier, mdessi, mrizzi, pcattana, rbobbitt, rhel-process-autobot, rojacob, simaishi, stcannon, watson-tool-maintainers, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Hickory DNS. The validating recursive resolver incorrectly processes Domain Name System Security Extensions (DNSSEC) Next Secure (NSEC) records by accepting parent-level records as proof that child domains do not exist. A remote attacker or rogue nameserver can exploit this vulnerability by providing forged negative responses, resulting in a Denial of Service (DoS) that prevents users from resolving legitimate domain names.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-11-08 02:01:59 UTC
Hickory DNS hickory-proto through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2 contain a DNSSEC validation flaw in the validating recursor's NSEC handler that accepts parent-side ancestor-delegation NSEC records as proof of nonexistence for names below the zone cut. An on-path attacker, rogue parent nameserver, or attacker winning a port and TXID race can deliver one forged NXDOMAIN response built from genuinely signed parent NSEC records, causing authenticated denial of existing child-zone names cached for the negative TTL.