Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution

{
  "id": "abf951b2c5c078c35aa3bb956f93bc18a0fbeb3f147b4bc83c92f484b9dfe671",
  "url": "https://osv.dev/vulnerability/CVE-2026-12039",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution",
    "summary": "Docker Sandboxes (sbx) enforces an HTTP/S-only egress allowlist but does not apply it to DNS resolution: the per-network embedded DNS server forwards any queried name to the host resolver whenever the network is internet-connected, without consulting the policy. A workload inside a sandbox, which the threat model treats as untrusted, can therefore encode data into DNS labels for an attacker-controlled domain and exfiltrate it through a DNS covert channel, bypassing the configured allowlist.",
    "evidence": "osv:CVE-2026-12039",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-12039",
      "aliases": [
        "CVE-2026-12039"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/docker/sbx-releases",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "e4809b108ff941fbd3dc8ab1edd8755af78ddc07"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0.13.0"
                      },
                      {
                        "fixed": "0.33.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "e4809b108ff941fbd3dc8ab1edd8755af78ddc07"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v0.33.0"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v0.31.0-rc1",
            "v0.30.0-rc2",
            "v0.30.0-rc1",
            "v0.30.0",
            "v0.29.0-rc1",
            "v0.29.0",
            "v0.28.3",
            "v0.28.2",
            "v0.28.1-rc2",
            "v0.28.1",
            "v0.28.0",
            "v0.27.0",
            "v0.26.1",
            "v0.25.0",
            "dev-ebc3fbe",
            "dev-e54ee33",
            "dev-dc73246",
            "dev-c7702ef",
            "dev-c13a59d",
            "dev-bad9503",
            "dev-ad0ca5e",
            "dev-a5207e0",
            "dev-921c1c7",
            "dev-8fc2763",
            "dev-793e764",
            "dev-78ed158",
            "dev-438ebd7",
            "dev-2631810",
            "dev-1f51dc0",
            "dev-02f174c",
            "v0.24.2",
            "v0.24.1",
            "v0.23.0",
            "v0.21.0",
            "v0.20.0",
            "v0.19.0",
            "v0.18.7",
            "v0.18.6",
            "v0.18.5",
            "v0.18.4",
            "v0.18.3",
            "v0.18.2",
            "v0.17.0",
            "v0.16.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-12039.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:25.774254421Z",
      "provider": "osv",
      "references": [
        "https://docs.docker.com/ai/sandboxes/",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/12xxx/CVE-2026-12039.json",
        "https://github.com/docker/sbx-releases/releases/tag/v0.33.0",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-12039"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-923"
        ],
        "cna_assigner": "Docker",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/12xxx/CVE-2026-12039.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-12039",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 492424,
  "published_at": "2026-06-18T13:48:14.682+00:00"
}