CVE-2026-56857: Root.Mkdir(All) can follow junctions out of the root on Windows in os
Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.
Generated by VEDAS. Scores as of 2026-11-08 00:03 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.
What it is
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).
Description quoted from the CVE record (assigned by Go, published 2026-10-08).
Weakness: CWE-1386 Insecure Operation on Windows Junction / Mount Point
How it can be exploited
Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA assessment (SSVC): CISA has no evidence of exploitation. Automatable: yes. Technical impact: total.
Public exploit evidence (Exploit Observer)
Exploit Observer has no public exploit code naming this CVE. Check Exploit Observer for anything new.
Live scores
- EPSS
- 0.006
low predicted chance of attack - VEDAS
- 0.047
little exploit evidence - On CISA KEV
- Not listed
- Detection rule
- No public rule yet
Who is affected
| Product | Affected | Not affected |
|---|---|---|
| Go standard library os | before 1.26.9 from 1.27.0-0 before 1.27.2 | Not stated |
| Go standard library internal/syscall/windows | before 1.26.9 from 1.27.0-0 before 1.27.2 | Not stated |
Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.
How to fix it
Fixed versions stated in the CVE record: 1.26.9, 1.27.2.
How to detect it
There is no open VEDAS detection rule for this bug yet. It is listed on the detection gaps page if CISA has confirmed attacks.
Advisories on this CVE
- Go 1.27.2 and 1.27.3: 15 security fixes including HTTP/2 server crashes, then a crypto/x509 distrust of the eMudhra intermediates (full advisory)
References
Other references
- https://go.dev/cl/847305
- https://go.dev/issue/81739
- https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
- https://pkg.go.dev/vuln/GO-2026-6604
Other databases
Where this comes from
This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.
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