# CVE-2026-123586: Hickory DNS query amplification in recursive resolver

Source: https://junglewise.ai/threats/cve-2026-123586-hickory-dns-0-25-0-alpha-3-through-0-25-2-contains-a-query  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-08. Updated: 2026-11-08  
License: CC BY 4.0 with a link back

CVE-2026-123586 · Severity: high · CVSS 7.5 · Published 2026-11-08

Hickory DNS is a DNS resolver library that translates domain names into IP addresses for applications. The vulnerability allows attackers who control two zones to trick the resolver into sending many repeated queries upstream, potentially exhausting resources and degrading DNS service availability. An attacker can trigger this by setting up zones with cyclic name server references and zero-TTL records.

Technologies: [Hickory-Dns Hickory-Recursor](https://junglewise.ai/threats/technologies/hickory-dns-hickory-recursor), [Hickory-Dns Hickory-Resolver](https://junglewise.ai/threats/technologies/hickory-resolver). Vendors: [Hickory-Dns](https://junglewise.ai/threats/vendors/hickory-dns).

## Quick answers

**Is CVE-2026-123586 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-123586 being exploited in the wild.

**How severe is CVE-2026-123586?** High severity, with a CVSS score of 7.5, published 8 November 2026.

**Which products and versions are affected?** Hickory-Dns Hickory-Recursor 0.25.0-alpha.3 through 0.25.2; Hickory-Dns Hickory-Resolver 0.26.0-alpha.1 through 0.26.1.

**Is there a fix for CVE-2026-123586?** Yes: fixed in hickory-resolver 0.26.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-123586 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-123586?** Check whether you run Hickory-Dns Hickory-Recursor or Hickory-Dns Hickory-Resolver at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in hickory-resolver 0.26.2

## Technical details

The recursive resolver fails to abort resolution promptly when encountering cyclic sibling domain name server referrals that lack glue records, causing uncontrolled recursion and exponential query amplification. An attacker controlling two zones with name servers in each other's zones (without glue records providing IP addresses) can exhaust the per-request query budget; zero-TTL NS records compound the amplification. The vulnerability affects Hickory DNS versions 0.25.0-alpha.3 through 0.25.2.

## Affected products

- Hickory DNS hickory-recursor 0.25.0-alpha.3 through 0.25.2
- Hickory DNS hickory-resolver 0.26.0-alpha.1 through 0.26.1

## Timeline

- 2026-09-03: disclosed
- 2026-11-08: advisory

## References

- [https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-cx5j-p54p-q756](https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-cx5j-p54p-q756)
- [https://www.vulncheck.com/advisories/hickory-dns-0.25.0-alpha.3-through-0.25.2-query-amplification-via-cyclic-referrals](https://www.vulncheck.com/advisories/hickory-dns-0.25.0-alpha.3-through-0.25.2-query-amplification-via-cyclic-referrals)

## Related threats

- [hickory-dns recursor glueless-NS referral amplification](https://junglewise.ai/threats/cve-2026-123606-the-hickory-dns-recursor-in-hickory-recursor-0-25-0-alpha-3)
- [Hickory DNS hickory-resolver unbounded retry loop resource exhaustion](https://junglewise.ai/threats/cve-2026-123604-hickory-dns-hickory-resolver-0-26-0-beta-1-before-0-26-2)
- [Hickory DNS IPv4-mapped IPv6 canonicalization bypass](https://junglewise.ai/threats/cve-2026-123603-hickory-proto-and-hickory-resolver-0-26-0-before-0-26-2-hickory)
- [Hickory DNS recursor cache poisoning via ghost domain attack](https://junglewise.ai/threats/cve-2026-123602-the-hickory-dns-recursor-in-all-versions-of-hickory-recursor-and)
- [Hickory DNS recursive resolver denial of service via cached empty connection pool](https://junglewise.ai/threats/cve-2026-123588-the-recursive-resolver-in-hickory-dns-all-versions-of-the)