GHSA-cvx7-x8pj-x2gw

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GHSA-cvx7-x8pj-x2gw

Summary: CoreDNS Vulnerable to DoQ Memory Exhaustion via Stream Amplification

Details: ### Summary A **Denial of Service (DoS)** vulnerability was discovered in the CoreDNS DNS-over-QUIC (DoQ) server implementation. The server previously created a new goroutine for every incoming QUIC stream without imposing any limits on the number of concurrent streams or goroutines. A remote, unauthenticated attacker could open a large number of streams, leading to uncontrolled memory consumption and eventually causing an Out Of Memory (OOM) crash — especially in containerized or memory-constrained environments. ### Impact - **Component**: `server_quic.go` - **Attack Vector**: Remote, network-based - **Attack Complexity**: Low - **Privileges Required**: None - **User Interaction**: None - **Impact**: High availability loss (OOM kill or unresponsiveness) This issue affects deployments with `quic://` enabled in the Corefile. A single attacker can cause the CoreDNS instance to become unresponsive using minimal bandwidth and CPU. ### Patches The patch introduces two key mitigation mechanisms: - **`max_streams`**: Caps the number of concurrent QUIC streams per connection. Default: `256`. - **`worker_pool_size`**: Introduces a server-wide, bounded worker pool to process incoming streams. Default: `1024`. This eliminates the 1:1 stream-to-goroutine model and ensures that CoreDNS remains resilient under high concurrency. The new configuration options are exposed through the `quic` Corefile block: ``` quic { max_streams 256 worker_pool_size 1024 } ``` These defaults are generous and aligned with typical DNS-over-QUIC client behavior. ### Workarounds If you're unable to upgrade immediately, you can: - Disable QUIC support by removing or commenting out the `quic://` block in your Corefile - Use container runtime resource limits to detect and isolate excessive memory usage - Monitor QUIC connection patterns and alert on anomalies ### References - [RFC 9250 - DNS over Dedicated QUIC Connections](https://datatracker.ietf.org/doc/html/rfc9250) - [quic-go GitHub project](https://github.com/quic-go/quic-go) - [QUIC stream exhaustion class of vulnerabilities (related)](https://www.usenix.org/conference/usenixsecurity23/presentation/botella) ### Credit Thanks to [@thevilledev](https://github.com/thevilledev) for disclovering this vulnerability and contributing a high-quality fix. ### For more information Please consult our [security guide](https://github.com/coredns/coredns/blob/master/.github/SECURITY.md) for more information regarding our security process.

References: https://github.com/coredns/coredns/security/advisories/GHSA-cvx7-x8pj-x2gw, https://nvd.nist.gov/vuln/detail/CVE-2025-47950, https://github.com/coredns/coredns/commit/efaed02c6a480ec147b1f799aab7cf815b17dfe1, https://datatracker.ietf.org/doc/html/rfc9250, https://github.com/coredns/coredns, https://github.com/quic-go/quic-go, https://www.usenix.org/conference/usenixsecurity23/presentation/botella