# CVE-2026-123588: Hickory DNS recursive resolver denial of service via cached empty connection pool

Source: https://junglewise.ai/threats/cve-2026-123588-the-recursive-resolver-in-hickory-dns-all-versions-of-the  
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-2026-123588 · Severity: high · CVSS 7.5 · Published 2026-11-08

Hickory DNS is a Rust-based DNS resolver library used to look up domain names and IP addresses on the internet. A flaw allows attackers to forge DNS responses that cause the resolver to cache an empty connection pool, making it unable to resolve any queries for an affected zone until the cache expires. This causes denial of service for applications relying on DNS lookups.

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-2026-123588 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-123588 being exploited in the wild.

**How severe is CVE-2026-123588?** High severity, with a CVSS score of 7.5, published 8 November 2026.

**Which products and versions are affected?** Hickory-Dns Hickory-Recursor all versions; Hickory-Dns Hickory-Resolver 0.26.0 before 0.26.2.

**Is there a fix for CVE-2026-123588?** 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-2026-123588 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-123588?** 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 properly validate glue records when following DNS referrals; if all lookups for nameserver IP addresses fail due to spoofed responses, it caches an empty connection pool. Any subsequent queries for that zone fail until the cache entry expires or is manually evicted. The attack requires network-level DNS spoofing capability and results in temporary but complete loss of DNS resolution for the targeted zone.

## Affected products

- Hickory DNS hickory-recursor all versions
- Hickory DNS hickory-resolver 0.26.0 before 0.26.2

## Timeline

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

## References

- [https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-9px7-7m25-f6q2](https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-9px7-7m25-f6q2)
- [https://www.vulncheck.com/advisories/hickory-dns-recursive-resolver-denial-of-service-via-cached-empty-connection-pool](https://www.vulncheck.com/advisories/hickory-dns-recursive-resolver-denial-of-service-via-cached-empty-connection-pool)

## 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 query amplification in recursive resolver](https://junglewise.ai/threats/cve-2026-123586-hickory-dns-0-25-0-alpha-3-through-0-25-2-contains-a-query)