CVE-2026-56857 Root.Mkdir(All) can follow junctions out of the root on Windows in os
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-56857?
CVE-2026-56857 is a critical vulnerability in Go standard library internal/syscall/windows, published on 8 Oct 2026.
Official 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).
Weakness: CWE-1386
Which versions are affected by CVE-2026-56857?
2 open source packages ship an affected version, including golang and stdlib.
| Package | Affected | Fixed in |
|---|---|---|
golang Bitnami | All versions | 1.26.9, 1.27.2 |
stdlib Go | All versions | 1.26.9, 1.27.2 |
How do I fix CVE-2026-56857?
Upgrade golang to a fixed version for your release line: 1.26.9 or 1.27.2.
Is CVE-2026-56857 being exploited?
There is no known exploitation of CVE-2026-56857 in the wild and no public exploit code.
Sources
Also known as AZL-107457, AZL-107489, BIT-golang-2026-56857, CLEANSTART-2026-BG25300, CLEANSTART-2026-FV74075, CLEANSTART-2026-HU64344 and 2202 more.