What’s Vulnerable › Vulnerabilities

CVE-2026-12039: Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution

• Severity: medium (CVSS 5.7 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-18 · updated 2026-10-26
• Weakness: CWE-923

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.

Affected products

• Docker Sandboxes: from 0.13.0 before 0.33.0 — fixed in 0.33.0

How to fix

Upgrade to a fixed version: Docker Sandboxes 0.33.0. Check the vendor advisory for mitigations.

References

• https://docs.docker.com/ai/sandboxes/
• https://github.com/docker/sbx-releases/releases/tag/v0.33.0

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