Vulnerability Intelligence Report
Root.Mkdir(All) can follow junctions out of the root on Windows in os
CVE-2026-56857
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).
No Active Exploit Signals
CVSS Base Score
9.8
CRITICAL
Exploitability:3.9
Impact Score:5.9
EPSS Probability:0.21%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
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Authentication
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Weaponization
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SSVC Action
—
Weaknesses (CWE)
CWE-1386 ↗CWE-1386: Insecure Operation on Windows Junction / Mount Point
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| Go standard library | os | 0 < 1.26.9 (affected), 1.27.0-0 < 1.27.2 (affected) |
| Go standard library | internal/syscall/windows | 0 < 1.26.9 (affected), 1.27.0-0 < 1.27.2 (affected) |
References & Technical Advisories
No reference links found.
Threat Intelligence Signals
EPSS Score
0.210%
GitHub Advisory
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | Go Project · Vendor · USA |
| Reserved | 2026-06-23T15:10:49 |
| Published | 2026-10-08T22:53:58 |
| Last Updated | 2026-10-09T15:36:01 |
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