# CVE-2026-123584: Hickory DNS UDP client denial of service via spoofed responses

Source: https://junglewise.ai/threats/cve-2026-123584-the-hickory-net-crate-in-hickory-dns-0-26-0-before-0-26-2-stops  
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-2026-123584 · Severity: medium · CVSS 5.9 · Published 2026-11-08

Hickory DNS is a DNS resolver library used by applications to look up domain names. A flaw in versions 0.26.0 and 0.26.1 allows remote attackers to crash DNS client connections by sending specially crafted malformed messages to the UDP port, even without knowing the transaction ID. This causes DNS lookups to fail, disrupting any application relying on the library for name resolution.

Technologies: [Hickory-Dns Hickory-Net](https://junglewise.ai/threats/technologies/hickory-dns-hickory-net). Vendors: [Hickory-Dns](https://junglewise.ai/threats/vendors/hickory-dns).

## Quick answers

**Is CVE-2026-123584 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-123584 being exploited in the wild.

**How severe is CVE-2026-123584?** Medium severity, with a CVSS score of 5.9, published 8 November 2026.

**Which products and versions are affected?** Hickory-Dns Hickory-Net 0.26.0 before 0.26.2.

**Is there a fix for CVE-2026-123584?** Yes: fixed in hickory-net 0.26.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-123584 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-123584?** Check whether you run Hickory-Dns Hickory-Net 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-net 0.26.2

## Technical details

The hickory-net crate improperly handles malformed DNS datagrams on UDP client connections; when a datagram cannot be parsed as a valid DNS message, the listener stops and returns an error rather than discarding the invalid packet and continuing. An attacker needs only to guess the source port (not the transaction ID) to spoof a malformed response that triggers this condition. This is a variant of the TuDoor attack that affects UDP DNS client availability.

## Affected products

- Hickory DNS hickory-net 0.26.0 before 0.26.2

## Timeline

- 2026-09-03: disclosed: GitHub Security Advisory GHSA-v44v-c8m4-gc43 published
- 2026-11-08: advisory: NVD entry CVE-2026-123584 published

## References

- [https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-v44v-c8m4-gc43](https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-v44v-c8m4-gc43)
- [https://www.vulncheck.com/advisories/hickory-dns-0.26.0-before-0.26.2-udp-client-denial-of-service-via-spoofed-responses](https://www.vulncheck.com/advisories/hickory-dns-0.26.0-before-0.26.2-udp-client-denial-of-service-via-spoofed-responses)

## Related threats

- [Hickory DNS NSEC3 closest-encloser proof unbounded loop](https://junglewise.ai/threats/cve-2026-123607-hickory-dns-hickory-proto-0-25-0-alpha-3-through-0-25-2-and)
- [Hickory DNS DNSSEC validation bypass via RRSIG Signer's Name](https://junglewise.ai/threats/cve-2026-123605-hickory-dns-hickory-proto-0-1-through-0-25-0-alpha-3-and-hickory)
- [Hickory DNS NSEC3 comparison operator inversion](https://junglewise.ai/threats/cve-2026-123601-hickory-dns-hickory-proto-0-25-0-through-0-26-0-alpha-1-and)
- [Hickory DNS DNSSEC validation bypass in NSEC3 NODATA](https://junglewise.ai/threats/cve-2026-123600-hickory-dns-hickory-proto-0-25-0-alpha-3-through-0-25-2-and)
- [Hickory DNS DNSSEC validation bypass in NSEC handler](https://junglewise.ai/threats/cve-2026-123596-hickory-dns-hickory-proto-through-0-26-0-alpha-1-and-hickory-net)