# CVE-2026-123570: hickory-proto DNS message parser memory amplification DoS

Source: https://junglewise.ai/threats/cve-2026-123570-the-dns-wire-format-message-parser-in-hickory-proto-hickory-dns  
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-2026-123570 · Severity: high · CVSS 7.5 · Published 2026-11-08

Hickory DNS is a Rust library used to parse and handle DNS messages. An attacker can send specially crafted DNS messages with extremely high record counts to force the parser to allocate approximately 18MB of memory per message, causing denial of service through resource exhaustion. This affects both DNS resolvers receiving responses and clients processing DNS data.

Technologies: [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-2026-123570 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-123570 being exploited in the wild.

**How severe is CVE-2026-123570?** High severity, with a CVSS score of 7.5, published 8 November 2026.

**Which products and versions are affected?** Hickory-Dns Hickory-Proto 0.18 before 0.26.2.

**Is there a fix for CVE-2026-123570?** 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-2026-123570 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-123570?** Check whether you run 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 0.26.2

## Technical details

The DNS wire-format parser in hickory-proto preallocates record vectors based on untrusted ANCOUNT, NSCOUNT, and ARCOUNT header fields before validating or reading the actual record data. By sending a UDP datagram with these counts set to 65535, an attacker forces allocation of ~270 bytes × 65535 elements (~18MB) per message. This CWE-770 vulnerability is exploitable remotely without authentication via UDP, and also affects resolvers via spoofed DNS responses.

## Affected products

- Hickory DNS hickory-proto 0.18 before 0.26.2

## Timeline

- 2026-09-03: disclosed: GitHub security advisory GHSA-67wc-6jq8-ghrc published
- 2026-11-08: advisory: CVE-2026-123570 assigned

## References

- [https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-67wc-6jq8-ghrc](https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-67wc-6jq8-ghrc)
- [https://www.vulncheck.com/advisories/hickory-dns-from-0.18-before-0.26.2-memory-amplification-dos-via-rr-counts](https://www.vulncheck.com/advisories/hickory-dns-from-0.18-before-0.26.2-memory-amplification-dos-via-rr-counts)

## 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)