Is CVE-2026-123604 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-123604 being exploited in the wild.

How severe is CVE-2026-123604?

High severity, with a CVSS score of 7.5, published 8 November 2026.

Which products and versions are affected?

Hickory-Dns Hickory-Resolver 0.26.0-beta.1 through 0.26.1.

Is there a fix for CVE-2026-123604?

Yes: fixed in 0.26.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-123604 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-123604?

Check whether you run 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.

CVE-2026-123604: Hickory DNS hickory-resolver unbounded retry loop resource exhaustion

CVE-2026-123604 · Severity: high · CVSS 7.5 · Published 2026-11-08

Hickory DNS is a DNS resolver library used by applications to perform domain name lookups. A vulnerability in its name server pool implementation allows a malicious DNS server to cause the resolver to enter an infinite retry loop, consuming CPU and memory resources until requests time out. This denial-of-service attack requires no authentication and can exhaust resolver capacity, disrupting DNS resolution for applications relying on affected versions.

Technologies: Hickory-Dns Hickory-Resolver. Vendors: Hickory-Dns.

Quick answers

Is CVE-2026-123604 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-123604 being exploited in the wild.
How severe is CVE-2026-123604?: High severity, with a CVSS score of 7.5, published 8 November 2026.
Which products and versions are affected?: Hickory-Dns Hickory-Resolver 0.26.0-beta.1 through 0.26.1.
Is there a fix for CVE-2026-123604?: Yes: fixed in 0.26.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-123604 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-123604?: Check whether you run 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: 0.26.2

Technical details

The NameServerPool::try_send function re-queues DNS requests with the TC (truncated) bit set to retry over TCP without checking which transport answered or implementing an iteration counter. A malicious authoritative nameserver can set TC=1 on every transport to trigger an unbounded loop that persists until the 5-second per-request deadline expires, exhausting resolver resources. The vulnerability affects hickory-resolver versions 0.26.0-beta.1 through 0.26.1 and is fixed in 0.26.2.

Affected products

Hickory DNS hickory-resolver 0.26.0-beta.1 through 0.26.1

Timeline

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

References

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