{"id":"CVE-2026-12039","aliases":["EUVD-2026-37892","GHSA-4crj-qc6g-g3xj"],"status":"published","title":"Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution","description":"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.","severity":{"version":"4.0","score":5.7,"vector":"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00103,"percentile":0.00993,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-923"],"published":"2026-06-18T13:48:14Z","modified":"2026-10-28T02:30:25Z","products":[{"vendor":"docker","product":"docker sandboxes"}],"references":[{"url":"https://docs.docker.com/ai/sandboxes/","tags":["product","web"]},{"url":"https://github.com/docker/sbx-releases/releases/tag/v0.33.0","tags":["release-notes","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-12039","tags":["advisory"]},{"url":"https://docs.docker.com/ai/sandboxes"},{"url":"https://github.com/advisories/GHSA-4crj-qc6g-g3xj"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/12xxx/CVE-2026-12039.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-12039","title":"Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution","description":"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.","status":"published","published":"2026-06-18T13:48:14.682Z","modified":"2026-08-13T13:33:35.581Z","cvss":[{"version":"4.0","score":5.7,"vector":"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","level":"medium","assessor":"cna"}],"cwes":["CWE-923"],"updated_at":"2026-11-02T14:19:48.461833Z"}],"euvd":[{"id":"EUVD-2026-37892","description":"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.","status":"published","published":"2026-06-18T13:48:14Z","modified":"2026-08-13T13:33:35Z","cvss":[{"version":"4.0","score":5.7,"vector":"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","level":"medium"}],"updated_at":"2026-11-02T18:01:56.761721Z"}],"ghsa":[{"id":"GHSA-4crj-qc6g-g3xj","title":"Docker Sandboxes (sbx) enforces an HTTP/S-only egress allowlist but does not apply it to DNS...","description":"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.","status":"published","published":"2026-06-18T15:32:02Z","modified":"2026-06-18T15:32:09Z","cvss":[{"version":"4.0","score":5.7,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium"}],"cwes":["CWE-923"],"updated_at":"2026-11-02T15:08:53.737891Z"}],"nvd":[{"id":"CVE-2026-12039","description":"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.","status":"published","published":"2026-06-18T14:17:20.78Z","modified":"2026-10-26T11:10:00.157Z","cvss":[{"version":"4.0","score":5.7,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"}],"cwes":["CWE-923"],"updated_at":"2026-11-02T14:12:24.912854Z"}],"osv":[{"id":"CVE-2026-12039","title":"Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution","description":"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.","status":"published","published":"2026-06-18T13:48:14.682Z","modified":"2026-10-28T02:30:25.774254421Z","cvss":[{"version":"4.0","score":5.7,"vector":"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","level":"medium"}],"cwes":["CWE-923"],"updated_at":"2026-11-02T15:44:57.354194Z"}]}}