# CVE-2026-123591: Hickory DNS DNSSEC validation bypass via missing RFC 6840 checks

Source: https://junglewise.ai/threats/cve-2026-123591-hickory-dns-hickory-net-0-26-0-beta-1-before-0-26-2-and-hickory  
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-2026-123591 · Severity: medium · CVSS 5.9 · Published 2026-11-08

Hickory DNS is a DNS resolver library used to look up and validate internet domain names. The library fails to properly validate DNSSEC signatures on certain delegation records, allowing attackers to forge DNS responses and redirect users to malicious servers or intercept sensitive communications.

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

## Quick answers

**Is CVE-2026-123591 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-123591 being exploited in the wild.

**How severe is CVE-2026-123591?** 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-beta.1 before 0.26.2; Hickory-Dns Hickory-Proto through 0.26.0-alpha.1.

**Is there a fix for CVE-2026-123591?** 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-2026-123591 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-123591?** Check whether you run Hickory-Dns Hickory-Net or Hickory-Dns Hickory-Proto 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 vulnerability is an insufficient verification of data authenticity (CWE-345) in DNSSEC validation logic. When validating insecure delegations, hickory-net and hickory-proto fail to check RFC 6840 §4.4 requirements: that NSEC/NSEC3 records proving no DS record exists must also prove the delegation's NS record exists. An attacker can reuse NSEC/NSEC3 records from the child zone to falsely prove an insecure delegation and forge other child zone records.

## Affected products

- Hickory DNS hickory-net 0.26.0-beta.1 before 0.26.2
- Hickory DNS hickory-proto through 0.26.0-alpha.1

## Timeline

- 2026-09-03: disclosed: GitHub security advisory published
- 2026-11-08: advisory: NVD entry published

## References

- [https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-7php-9j59-g3ch](https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-7php-9j59-g3ch)
- [https://www.vulncheck.com/advisories/hickory-dns-0.26.0-beta.1-before-0.26.2-dnssec-validation-bypass-via-missing-rfc-6840-checks](https://www.vulncheck.com/advisories/hickory-dns-0.26.0-beta.1-before-0.26.2-dnssec-validation-bypass-via-missing-rfc-6840-checks)

## Related threats

- [Hickory DNS hickory-proto denial of service in BinEncoder](https://junglewise.ai/threats/cve-2026-123608-hickory-dns-hickory-proto-from-0-3-1-before-0-26-1-contains-a)
- [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 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 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)