CVE-2026-42306

Host file overwrite via docker cp symlink race

Published Jun 12, 2026 · Updated Jun 12, 2026

TOCTOU race in Moby Docker Engine before 29.5.1 allows local users controlling a container to overwrite arbitrary host files. During docker cp mount setup, the daemon resolves a container-relative volume destination to a host path, then mount() follows a symlink swapped in before use. Exploitation requires a mounted volume, rapid symlink replacement by a container process, and an operator's copy or archive API request; read-only volumes instead mask the host path and interrupt service.

CVSS severity7.2
High
EPSS probability0.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

TOCTOU race in Moby Docker Engine before 29.5.1 allows local users controlling a container to overwrite arbitrary host files. During docker cp mount setup, the daemon resolves a container-relative volume destination to a host path, then mount() follows a symlink swapped in before use. Exploitation requires a mounted volume, rapid symlink replacement by a container process, and an operator's copy or archive API request; read-only volumes instead mask the host path and interrupt service.

The record

CVE
CVE-2026-42306
Published
Jun 12, 2026
Updated
Jun 12, 2026
Vendor
Moby Project
Product
Moby
Classifications
CWE-367, CWE-61, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 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=Docker Engine < 29.5.1
  2. Affected versionversion=github.com/docker/docker/daemon <= 28.5.2
  3. Affected versionversion=github.com/moby/moby/v2/daemon < 2.0.0-beta.14

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Moby Project · Mobyversion=Docker Engine < 29.5.1; version=github.com/docker/docker/daemon <= 28.5.2; version=github.com/moby/moby/v2/daemon < 2.0.0-beta.14

Published CVSS scores

7.2GitHub, Inc.CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:N/I:H/A:H

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-367Time-of-check Time-of-use (TOCTOU) Race Condition
CWE-61UNIX Symbolic Link (Symlink) Following
T1068Exploitation for Privilege Escalation

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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