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.
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Thu, 18 Jun 2026 16:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution | |
| Weaknesses | CWE-923 | |
| References |
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| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: Docker
Published:
Updated: 2026-06-18T15:00:24.095Z
Reserved: 2026-06-11T19:23:44.967Z
Link: CVE-2026-12039
Updated: 2026-06-18T15:00:11.463Z
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