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GHSA-527x-5wrf-22m2
No affected components available
Multiple CoreDNS server implementations (gRPC, HTTPS, and HTTP/3) lack critical resource-limiting controls. An unauthenticated remote attacker can exhaust memory and degrade or crash the server by opening many concurrent connections, streams, or sending oversized request bodies. The issue is similar in nature to CVE-2025-47950 (QUIC DoS) but affects additional server types that do not enforce connection limits, stream limits, or message size constraints.
Impact
1. Missing connection and stream limits (gRPC / HTTPS / HTTP3)
The affected servers do not enforce reasonable upper bounds on concurrent connections or active streams. An attacker can:
- Open many parallel connections
- Rapidly issue requests without limit
- Consume memory until the CoreDNS process becomes unresponsive or is terminated by the OOM killer
Testing demonstrates that modest resource configurations (e.g., 256 MB RAM) can be exhausted quickly. Increasing concurrency parameters in the PoCs allows attackers to scale the impact.
2. Missing message-size validation in the gRPC server
The gRPC server accepts arbitrarily large protobuf messages (default limit ~4 MB per request) without validating against DNS protocol constraints (maximum 64 KB). Sending multiple concurrent oversized messages can quickly exhaust available memory.
This vulnerability mirrors earlier hardening work in PR https://github.com/coredns/coredns/pull/7490, which applied checks for upstream proxying but left server-side request validation unprotected.
Result:
In all cases, remote unauthenticated attackers can reliably trigger memory exhaustion and cause a denial of service.
Patches
v1.14.0
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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