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VulnerabilityPublished Updated

CVE-2026-12039: Docker Sandboxes · Improper Restriction of Communication Channel to Intended Endpoints

Affects Docker SandboxesSource CVE Database V5

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Not known to be exploited · CVSS 5.7 Medium : upgrade to 0.33.0 when convenient.

Data as of 1 Nov 2026, 08:20 UTC

CVSS 4.0 base score
5.7Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 0% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.33.0
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 18 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.

What to do

Upgrade Docker Sandboxes to 0.33.0.

Affected software

ProductAffectedFixed in
DockerDocker SandboxesAffected
  • >=0.13.0 <0.33.0
Fixed in
  • 0.33.0
GitHubdocker/sbx-releasespkg:github/docker/sbx-releasesOther threatsAffected
  • =0.13.0
Fixed in–

CPE configurations (1)

  • cpe:2.3:a:docker:docker_sandboxes:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

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.

References

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