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Vulnerabilities CVE-2026-12039

CVE-2026-12039

Medium
Open
TLP:CLEAR

Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution

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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.

Details

CVSS Score
5.7
EPSS Score
0.15%

4.5th percentile

CVSS 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
Confidence
90%
Published
Jun 18, 2026
Last Modified
Aug 13, 2026
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