CVE-2026-123586
Received Received - Intake

Hickory DNS Recursive Resolver Query Amplification Flaw

Publication date: 2026-11-08

Last updated on: 2026-11-08

Assigner: VulnCheck

Description
Hickory DNS 0.25.0-alpha.3 through 0.25.2 contains a query amplification vulnerability in its recursive resolver, which mishandles cyclic sibling name server referrals that lack glue records. Attackers controlling two zones whose name servers reference each other without glue records can make the recursor loop, sending many upstream queries, amplified further by zero-TTL NS records.

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Meta Information

Published
2026-11-08
Last Modified
2026-11-08
Generated
2026-11-08
AI Q&A
2026-11-08
EPSS Evaluated
N/A
NVD
CVE-2026-123586
EUVD
EUVD-2026-119345

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
hickory_dns hickory_dns From 0.25.0_alpha.3 (inc) to 0.25.2 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-400 The product does not properly control the allocation and maintenance of a limited resource.

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Executive Summary

This is a query amplification vulnerability in Hickory DNS versions 0.25.0-alpha.3 through 0.25.2 where cyclic sibling name server referrals without glue records cause the recursive resolver to enter an infinite loop. Attackers controlling two zones with mutually referencing name servers can exploit this to generate excessive upstream queries, amplified further by zero-TTL NS records.

Detection Guidance

Monitor DNS resolver logs for excessive upstream queries or loops. Check for cyclic sibling domain referrals without glue records in DNS responses. Use tools like tcpdump or Wireshark to capture and analyze DNS traffic for unusual query patterns or repeated requests to the same domains.

Impact Analysis

This vulnerability can lead to uncontrolled resource consumption on the DNS resolver, causing high CPU and memory usage. It may result in service degradation or outages due to excessive upstream queries, potentially affecting network performance and availability.

Mitigation Strategies

Disable the Hickory DNS recursive resolver if not essential. Block or filter DNS queries involving cyclic sibling referrals without glue records at the network perimeter. Monitor for signs of exploitation and update to a patched version once available.

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