Medium

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

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.

Published Jun 18, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Docker

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.1% (30-day exploitation probability)+0
Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.1%

ahead of 1% of scored CVEs · Oct 15, 2026

Affects

Docker

Docker Sandboxes

CVSS base

5.7

Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Docker Docker Sandboxes).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Docker	Docker Sandboxes	≥ 0.13.0 and < 0.33.0	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Attack requirements

Present

Privileges required

Low

User interaction

None

Scope

Confidentiality (vulnerable system)

High

Integrity (vulnerable system)

None

Availability (vulnerable system)

None

Confidentiality (subsequent)

None

Integrity (subsequent)

None

Availability (subsequent)

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.7	CVSS 4.0	Medium	—	—	security@docker.com via NIST National Vulnerability Database
5.7	CVSS 4.0	Medium	—	—	Docker via CVE Program (cve.org) e CISA ADP

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

(score shown at the top: security@docker.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-923

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.10%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.

endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · docker/docker sandboxes
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 5.7
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Awaiting Analysis
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Jun 18, 2026 · Docker

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

2 on the record

docs.docker.com/ai/sandboxes/
product, NIST National Vulnerability Database
github.com/docker/sbx-releases/releases/tag/v0.33.0
release-notes, NIST National Vulnerability Database

Elsewhere on this site

Docker
every CVE for this vendor

CWE-923
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-105570 Docker Sandboxes OAuth response masking could be bypassed with a case-variant token host 7d
Medium CVE-2026-101998 Fail-open response masking in Docker Sandboxes can expose proxy-managed credentials 7d
Medium CVE-2026-105452 Docker Sandboxes egress proxy could forward unrecognized client credentials to managed hosts 7d
High CVE-2026-79994 Docker Sandboxes UDS forwarder can reach arbitrary host Unix sockets through a symlink race Sep 15, 2026
Critical CVE-2026-77179 Docker Sandboxes guest can write arbitrary macOS host files via a symlink in the virtio-fs stored-path fallback Sep 15, 2026
High CVE-2026-17106 Tar extraction in moby/go-archive can write outside the destination directory via link following Aug 18, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-12039 is "Docker Sandboxes network egress allowlist bypass via unfiltered DNS resolution", rated Medium. It affects Docker Sandboxes (Docker); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.7 describes technical severity. EPSS 0.10% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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