CVE-2026-12039

Data exfiltration via unfiltered DNS resolution

Published Jun 18, 2026 · Updated Jun 18, 2026

Improper network-policy enforcement in Docker Sandboxes before 0.33.0 allows local users to exfiltrate data through DNS queries. The embedded DNS server forwards sandbox queries to the host resolver whenever the sandbox network is internet-connected, without checking the HTTP/S egress allowlist. An untrusted workload with low privileges must run inside an internet-connected sandbox and can encode confidential data in labels under an attacker-controlled domain.

CVSS severity5.7
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper network-policy enforcement in Docker Sandboxes before 0.33.0 allows local users to exfiltrate data through DNS queries. The embedded DNS server forwards sandbox queries to the host resolver whenever the sandbox network is internet-connected, without checking the HTTP/S egress allowlist. An untrusted workload with low privileges must run inside an internet-connected sandbox and can encode confidential data in labels under an attacker-controlled domain.

The record

CVE
CVE-2026-12039
Published
Jun 18, 2026
Updated
Jun 18, 2026
Vendor
Docker
Product
Docker Sandboxes
Classifications
CWE-923, CAPEC-554, T1048.003
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.13.0 <0.33.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Docker · Docker Sandboxesversion=0.13.0 <0.33.0

Published CVSS scores

5.7Docker Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-923Improper Restriction of Communication Channel to Intended Endpoints
CAPEC-554Functionality Bypass
T1048.003Exfiltration Over Unencrypted Non-C2 Protocol

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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