What’s Vulnerable › Vulnerabilities

CVE-2026-32936: CoreDNS DoH GET path missing size validation causes CPU and memory amplification

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-05-05 · updated 2026-07-25
• Weakness: CWE-400

Description

CoreDNS is a DNS server that chains plugins. In versions prior to 1.14.3, the DNS-over-HTTPS (DoH) GET path accepts oversized dns= query parameter values and performs URL query parsing, base64 decoding, and DNS message unpacking before rejecting the request. Unlike the POST path, which applies a bounded read via http.MaxBytesReader limited to 65536 bytes, the GET path has no equivalent size validation before expensive processing. A remote, unauthenticated attacker can repeatedly send oversized DoH GET requests to force high CPU usage, large transient memory allocations, and elevated garbage-collection pressure, leading to denial of service. This issue has been fixed in version 1.14.3.

Affected products

• coredns: before 1.14.3 — fixed in 1.14.3

How to fix

Upgrade to a fixed version: coredns 1.14.3. Check the vendor advisory for mitigations.

References

• https://github.com/coredns/coredns/releases/tag/v1.14.3
• https://github.com/coredns/coredns/security/advisories/GHSA-63cw-r7xf-jmwr
• https://github.com/coredns/coredns/security/advisories/GHSA-63cw-r7xf-jmwr

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