GHSA-CVX7-X8PJ-X2GW

Vulnerability from github – Published: 2025-06-06 21:27 – Updated: 2025-06-09 21:39
VLAI
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

Credit

Thanks to @thevilledev for disclovering this vulnerability and contributing a high-quality fix.

For more information

Please consult our security guide for more information regarding our security process.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/coredns/coredns"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.12.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-47950"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-06-06T21:27:27Z",
    "nvd_published_at": "2025-06-06T18:15:35Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nA **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 \u2014 especially in containerized or memory-constrained environments.\n\n### Impact\n\n- **Component**: `server_quic.go`\n- **Attack Vector**: Remote, network-based\n- **Attack Complexity**: Low\n- **Privileges Required**: None\n- **User Interaction**: None\n- **Impact**: High availability loss (OOM kill or unresponsiveness)\n\nThis 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.\n\n### Patches\n\nThe patch introduces two key mitigation mechanisms:\n\n- **`max_streams`**: Caps the number of concurrent QUIC streams per connection. Default: `256`.\n- **`worker_pool_size`**: Introduces a server-wide, bounded worker pool to process incoming streams. Default: `1024`.\n\nThis 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:\n\n```\nquic {\n    max_streams 256\n    worker_pool_size 1024\n}\n```\n\nThese defaults are generous and aligned with typical DNS-over-QUIC client behavior.\n\n### Workarounds\n\nIf you\u0027re unable to upgrade immediately, you can:\n- Disable QUIC support by removing or commenting out the `quic://` block in your Corefile\n- Use container runtime resource limits to detect and isolate excessive memory usage\n- Monitor QUIC connection patterns and alert on anomalies\n\n### References\n\n- [RFC 9250 - DNS over Dedicated QUIC Connections](https://datatracker.ietf.org/doc/html/rfc9250)\n- [quic-go GitHub project](https://github.com/quic-go/quic-go)\n- [QUIC stream exhaustion class of vulnerabilities (related)](https://www.usenix.org/conference/usenixsecurity23/presentation/botella)\n\n### Credit\n\nThanks to [@thevilledev](https://github.com/thevilledev) for disclovering this vulnerability and contributing a high-quality fix.\n\n### For more information\n\nPlease consult our [security guide](https://github.com/coredns/coredns/blob/master/.github/SECURITY.md) for more information regarding our security process.",
  "id": "GHSA-cvx7-x8pj-x2gw",
  "modified": "2025-06-09T21:39:31Z",
  "published": "2025-06-06T21:27:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/coredns/coredns/security/advisories/GHSA-cvx7-x8pj-x2gw"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-47950"
    },
    {
      "type": "WEB",
      "url": "https://github.com/coredns/coredns/commit/efaed02c6a480ec147b1f799aab7cf815b17dfe1"
    },
    {
      "type": "WEB",
      "url": "https://datatracker.ietf.org/doc/html/rfc9250"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/coredns/coredns"
    },
    {
      "type": "WEB",
      "url": "https://github.com/quic-go/quic-go"
    },
    {
      "type": "WEB",
      "url": "https://www.usenix.org/conference/usenixsecurity23/presentation/botella"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "CoreDNS Vulnerable to DoQ Memory Exhaustion via Stream Amplification"
}



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