CVE-2026-12039

Medium

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.

SeverityMedium

CVSS5.7

Exploit probability—

Product

Docker Sandboxes

PublishedJun 18, 2026

First seenJun 18, 2026

Weakness typeCWE-923CWE-923

How to fix

Update

docker docker_sandboxes0.33.0 or later

Vendor advisories

github.com/docker/sbx-releases/releases/tag/v0.33.0

Affected products

Product	Affected versions	Fixed in
docker docker_sandboxes	0.13.0 ≤ v < 0.33.0	0.33.0

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