Go os Root.Mkdir can follow junctions outside the root on Windows
Priority MEDIUM 50CWE-1386Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 5 fixed, 85 without a fix
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat.
Summary
The Go standard library os and internal/syscall/windows packages are affected before 1.26.9 and from 1.27.0-0 before 1.27.2. On Windows, when the last path component is a junction pointing to an empty location, Root directory creation can create a directory at the junction target even when that target is outside the root (CWE-1386). An unauthenticated remote attacker can trigger this without user interaction.
Written with Claude Haiku 5.5 from the sources below · 2026-11-07
Description from the CNA
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).
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00553 46th percentileScored 2026-11-07
Fix Partial os (Go standard library): 1.26.9, 1.27.2internal/syscall/windows (Go standard library): 1.26.9, 1.27.2Red Hat: 5 advisoriesRed Hat: 5 fixed, 85 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Go standard library | os | before 1.26.9; 1.27.0-0 to before 1.27.2 | 1.26.9, 1.27.2 | Patch available | CNA |
| Go standard library | internal/syscall/windows | before 1.26.9; 1.27.0-0 to before 1.27.2 | 1.26.9, 1.27.2 | Patch available | CNA |
- os VendorGo standard library Affected before 1.26.9; 1.27.0-0 to before 1.27.2 Fixed in 1.26.9, 1.27.2 Patch available CNA
- internal/syscall/windows VendorGo standard library Affected before 1.26.9; 1.27.0-0 to before 1.27.2 Fixed in 1.26.9, 1.27.2 Patch available CNA
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:golang:go:*:*:*:*:*:*:*:* | — | — | Go standard library |
- cpe:2.3:a:golang:go:*:*:*:*:*:*:*:* Versions — — ·Go standard library
Remediation
Upgrade Go to 1.26.9 or 1.27.2 for the os and internal/syscall/windows packages. Red Hat fixes it in OpenShift Service Mesh 3.0.17 (RHSA-2026:92451), 3.1.14 (RHSA-2026:92480), 3.2.11 (RHSA-2026:92497), 3.3.9 (RHSA-2026:92509) and 3.4.4 (RHSA-2026:92516). Red Hat lists AWS Load Balancer Operator and other products as affected without a fix.
Written with Claude Haiku 5.5 from the sources below · 2026-11-07
- Fix · CNA os (Go standard library) Fixed in 1.26.9, 1.27.2
- Fix · CNA internal/syscall/windows (Go standard library) Fixed in 1.26.9, 1.27.2
Red Hat 5 advisories
- RHSA-2026:92516 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.4.4
- Red Hat OpenShift Service Mesh 3.4 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
- RHSA-2026:92509 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.3.9
- Red Hat OpenShift Service Mesh 3.3 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
- RHSA-2026:92497 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.2.11
- Red Hat OpenShift Service Mesh 3.2 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
Show 2 more Red Hat advisories
- RHSA-2026:92480 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.1.14
- Red Hat OpenShift Service Mesh 3.1 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
- RHSA-2026:92451 Released 2026-10-29 · Red Hat rating ImportantRed Hat OpenShift Service Mesh 3.0.17
- Red Hat OpenShift Service Mesh 3.0 registry.redhat.io/openshift-service-mesh/istio-cni-rhel9, registry.redhat.io/openshift-service-mesh/istio-pilot-rhel9, registry.redhat.io/openshift-service-mesh/istio-proxyv2-rhel9 +1
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| AWS Load Balancer Operator | Affected | — |
| Ansible Automation Orchestrator 2026 | Affected | — |
| Assisted Installer for Red Hat OpenShift Container Platform 2 | Affected | — |
| Builds for Red Hat OpenShift | Affected | — |
| Compliance Operator | Affected | — |
| Confidential Compute Attestation | Affected | — |
| Cost Management Metrics Operator | Affected | — |
| Cost Management On Premise | Affected | — |
| Cryostat 4 | Affected | — |
| Custom Metric Autoscaler operator for Red Hat Openshift | Affected | — |
| DPU kit for NVIDIA | Affected | — |
| Deployment Validation Operator | Affected | — |
| Exploit Intelligence | Affected | — |
| External Secrets Operator for Red Hat OpenShift | Affected | — |
| Fence Agents Remediation Operator | Affected | — |
| File Integrity Operator | Affected | — |
| Gatekeeper 3 | Affected | — |
| Helm CLI for Red Hat OpenShift | Affected | — |
| Logging Subsystem for Red Hat OpenShift | Affected | — |
| Logical Volume Manager Storage | Affected | — |
| Machine Deletion Remediation Operator | Affected | — |
| Migration Toolkit for Applications 8 | Affected | — |
| Migration Toolkit for Containers | Affected | — |
| Multiarch Tuning Operator | Affected | — |
| Multicluster Engine for Kubernetes | Affected | — |
| Multicluster Global Hub | Affected | — |
| Multicluster Global Hub 5 | Affected | — |
| Network Observability Operator | Affected | — |
| Node HealthCheck Operator | Affected | — |
| Node Maintenance Operator | Affected | — |
| Nvidia GPU Driver for RHEL on Openshift | Affected | — |
| OpenShift API for Data Protection | Affected | — |
| OpenShift Developer Tools and Services | Affected | No fix planned: Out of support scope |
| OpenShift Lightspeed | Affected | — |
| OpenShift Pipelines | Affected | No fix yet: Fix deferred |
| OpenShift Serverless | Affected | No fix yet: Fix deferred |
| OpenShift Service Mesh 3 | Affected | No fix yet |
| OpenShift Source-to-Image (S2I) | Affected | — |
| Red Hat 3scale API Management Platform 2 | Affected | — |
| Red Hat AMQ Clients | Affected | No fix yet: Fix deferred |
| Red Hat Advanced Cluster Management for Kubernetes 2 | Affected | — |
| Red Hat Advanced Cluster Security 4 | Affected | — |
| Red Hat Ansible Automation Platform 2 | Affected | — |
| Red Hat Ceph Storage 5 | Affected | — |
| Red Hat Ceph Storage 6 | Affected | — |
| Red Hat Ceph Storage 7 | Affected | — |
| Red Hat Ceph Storage 8 | Affected | — |
| Red Hat Ceph Storage 9 | Affected | — |
| Red Hat Connectivity Link 1 | Affected | — |
| Red Hat Developer Hub 1 | Affected | — |
| Red Hat Edge Manager 1 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat Lightspeed for Runtimes Operator | Affected | — |
| Red Hat OpenShift AI (RHOAI) | Affected | — |
| Red Hat OpenShift Cluster Manager CLI | Affected | — |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Dev Spaces | Affected | — |
| Red Hat OpenShift Dev Workspaces Operator | Affected | — |
| Red Hat OpenShift GitOps | Affected | — |
| Red Hat OpenShift Virtualization 4 | Affected | No fix yet |
| Red Hat OpenShift Virtualization 5 | Affected | — |
| Red Hat OpenShift distributed tracing 3 | Affected | — |
| Red Hat OpenShift for Windows Containers | Affected | — |
| Red Hat OpenShift on AWS | Affected | No fix yet: Fix deferred |
| Red Hat OpenStack Platform 16.2 | Affected | — |
| Red Hat OpenStack Platform 17.1 | Affected | — |
| Red Hat OpenStack Platform 18.0 | Affected | — |
| Red Hat Openshift Data Foundation 4 | Affected | — |
| Red Hat Quay 3 | Affected | — |
| Red Hat Satellite 6 | Affected | No fix yet: Fix deferred |
| Red Hat Service Interconnect 2 | Affected | No fix yet: Fix deferred |
| Red Hat Trusted Artifact Signer | Affected | — |
| Red Hat Web Terminal | Affected | — |
| Secrets Management Console for Red Hat OpenShift | Affected | — |
| Security Profiles Operator | Affected | — |
| Self-service automation portal 2 | Affected | — |
| Service Telemetry Framework 1.5 | Affected | — |
| Zero Trust Workload Identity Manager | Affected | — |
| Zero Trust Workload Identity Manager - Tech Preview | Affected | — |
| cert-manager Operator for Red Hat OpenShift | Affected | — |
| mirror registry for Red Hat OpenShift 2 | Affected | — |
| streams for Apache Kafka 2 | Affected | No fix planned: Out of support scope |
| streams for Apache Kafka 3 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Service Mesh 3.0 | Fixed | RHSA-2026:92451 |
| Red Hat OpenShift Service Mesh 3.1 | Fixed | RHSA-2026:92480 |
| Red Hat OpenShift Service Mesh 3.2 | Fixed | RHSA-2026:92497 |
| Red Hat OpenShift Service Mesh 3.3 | Fixed | RHSA-2026:92509 |
| Red Hat OpenShift Service Mesh 3.4 | Fixed | RHSA-2026:92516 |
Not affected: 17 products
- Red Hat Ansible Automation Platform 2
- Red Hat Certification Program for Red Hat Enterprise Linux 9
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat Enterprise Linux AI (RHEL AI) 3
- Red Hat OpenShift AI (RHOAI)
- Red Hat OpenShift Service Mesh 3.0
- Red Hat OpenShift Service Mesh 3.1
- Red Hat OpenShift Service Mesh 3.2
- Red Hat OpenShift Service Mesh 3.3
- Red Hat OpenShift Service Mesh 3.4
- Red Hat OpenStack Platform 13 (Queens)
- Red Hat OpenStack Platform 16.2
- Red Hat OpenStack Platform 17.1
- Red Hat OpenStack Platform 18.0
Timeline
- 2026-10-09 Threatist record created from CVE-2026-56857
- 2026-10-09 Alias added: GHSA-c3q7-m35p-9qq7
- 2026-10-10 CVSS score added · CISA ADP
- 2026-10-10 Weakness changed · CISA ADP
- 2026-10-10 CISA SSVC decision points changed
- 2026-10-10 Priority changed: LOW → MEDIUM
- 2026-10-23 Affected versions changed · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92451 · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92509 · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92497 · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92480 · Red Hat
- 2026-10-30 Fix available: Red Hat OpenShift Service Mesh 3.0, Red Hat OpenShift Service Mesh 3.1, Red Hat OpenShift Service Mesh 3.2 +1 · Red Hat
- 2026-10-30 Affected versions changed · Red Hat
- 2026-10-31 Fix available: RHSA-2026:92516 · Red Hat
- 2026-10-31 Fix available: Red Hat OpenShift Service Mesh 3.4 · Red Hat
- 2026-11-07 Affected versions changed · Red Hat
References
More Go standard library vulnerabilities
- TI-2020-00578 Improper certificate validation in Microsoft Windows KEVCVSS 3.1HIGH 8.1
- TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
- TI-2023-24278 HTTP/2 CONTINUATION flood in net/http CVSS 3.1HIGH 7.5
- TI-2018-05208 The "go get" implementation in Go 1.9.4, when the -insecure command-line option is used… CVSS 3.1HIGH 8.8
- TI-2024-16309 Panic when parsing invalid palette-color images in golang.org/x/image CVSS 3.1HIGH 7.5
- TI-2022-20112 Request smuggling due to improper request handling in golang.org/x/net/http2/h2c CVSS 3.1HIGH 7.5
Sources
- CVE-2026-56857 · CVE Program
- CVE-2026-56857 · NVD
- FIRST EPSS
- GHSA-c3q7-m35p-9qq7 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-56857 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences