CVE-2026-56857

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

CVE-2026-56857 is fixed in 4 products on 2 platforms, first by Go Programming Language 1.27.3, released October 19, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

UrgentFixed on 2 platforms

CVSS

9.8

Critical

Exploitation

None reported

No vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0055

46th percentile

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).

Where it's fixed

Product	Fixed in	Fix	Released
Windows apps
Go Programming Language	1.27.3	Go Programming Language 1.27.3	Oct 19, 2026
Linux
go1.26 · opensuse-leap 16.0	1.26.9-160000.1.1	OPENSUSE-SU-2026:22095-1	Nov 7, 2026
go1.26 · sles 15.6	1.26.9-150000.1.33.1	SUSE-SU-2026:4629-1	Nov 7, 2026
go1.26 · sles 15.7	1.26.9-150000.1.33.1	SUSE-SU-2026:4629-1	Nov 7, 2026
go1.26 · sles 16.0	1.26.9-160000.1.1	SUSE-SU-2026:24239-1	Nov 7, 2026
go1.26-openssl · sles 15.6	1.26.10-150600.13.18.1	SUSE-SU-2026:4866-1	Nov 7, 2026
go1.26-openssl · sles 15.7	1.26.10-150600.13.18.1	SUSE-SU-2026:4866-1	Nov 7, 2026
go1.27 · opensuse-leap 16.0	1.27.2-160000.1.1	OPENSUSE-SU-2026:22093-1	Nov 7, 2026
go1.27 · sles 15.6	1.27.2-150000.1.12.1	SUSE-SU-2026:4625-1	Nov 7, 2026
go1.27 · sles 15.7	1.27.2-150000.1.12.1	SUSE-SU-2026:4625-1	Nov 7, 2026
go1.27 · sles 16.0	1.27.2-160000.1.1	SUSE-SU-2026:24237-1	Nov 7, 2026

Details

Published
October 8, 2026
Weakness
Insecure Operation on Windows Junction / Mount Point
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56857

For tools and AI agents

This page as data: JSON · Markdown

Link to this page

If this page saved you time, a link to it in your ticket, advisory or write-up helps others find it.

HTML

<a href="https://patchblox.com/security/cve/CVE-2026-56857">CVE-2026-56857 on Patchblox Patch Radar</a>

Reusing the data? How to credit Patch Radar.

Is this on your machines?

Patchblox finds every install below the fixed version on Windows, macOS and Linux, and updates them through your release rings.

Get a demo

Patch Radar data is free to use with attribution. Terms and how to credit it.

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.