Vulnerability · Published Jun 18, 2026 · Assigned by Docker
CVE-2026-12039Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution
Medium 5.7
In plain English
A medium-severity security flaw in Docker Sandboxes from Docker. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 1% of all known vulnerabilities).
Official 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 (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Docker | Docker Sandboxes | 0.13.0 – before 0.33.0 |
Weakness: CWE-923 · 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