CVE-2026-56857

Root.Mkdir(All) can follow junctions out of the root on Windows in os

Published Oct 8, 2026 CVSS 3.1 · 9.8 Critical EPSS < 1% KEV · Not listed
Description
On Windows, when the target of Root.Mkdir or Root.MkdirAll is a junction pointing to an empty location, the operation can create a directory at the junction target even when that target is located outside the root. This only applies to operations where the last path component is a junction (path/to/junction, but not path/junction/target).

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Weaknesses CWE-1386
Metrics cvssV3_1

{'score': 3.3, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-22
Type Values Removed Values Added
Weaknesses CWE-59
References
Metrics threat_severity

None

cvssV3_1

{'score': 3.3, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N'}

threat_severity

Low

Type Values Removed Values Added
First Time appeared Go Standard Library
Go Standard Library internal/syscall/windows
Go Standard Library os
Vendors & Products Go Standard Library
Go Standard Library internal/syscall/windows
Go Standard Library os
Type Values Removed Values Added
Weaknesses CWE-22
Type Values Removed Values Added
Description On Windows, when the target of Root.Mkdir or Root.MkdirAll is a junction pointing to an empty location, the operation can create a directory at the junction target even when that target is located outside the root. This only applies to operations where the last path component is a junction (path/to/junction, but not path/junction/target).
Title Root.Mkdir(All) can follow junctions out of the root on Windows in os
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Go
Published
Updated
Oct 9, 2026, 3:36 PM
Reserved
Jun 23, 2026, 3:10 PM
Status
Awaiting Analysis
Published
Oct 8, 2026, 11:17 PM
Modified
Oct 9, 2026, 4:35 PM
Severity
Low
Public date
Oct 8, 2026, 10:53 PM