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GHSA-rqfv-2mw9-78g2

CriticalCVSS 10 / 10
Published Sep 11, 2026·Last modified Sep 11, 2026
Affected Components(1)
PyPI logomysql-mcp-server
< 0.4.2
Description

Summary

In SSE/HTTP transport mode, mysql_mcp_server constructs SseServerTransport without passing security_settings. As a result, the MCP Python SDK's DNS-rebinding protection (Origin/Host header validation) is disabled; the Starlette application has no CORS or TrustedHost middleware; and the service binds to 0.0.0.0 by default with no authentication on any route.

Trigger condition: MCP_TRANSPORT=sse. The default stdio mode is not affected.

Attack Scenarios

Scenario A — Direct exposure: Any network attacker can invoke execute_sql to run arbitrary SQL without credentials → full data dump, and via MySQL FILE privileges, arbitrary file read/write and RCE.

Scenario B — DNS rebinding (local bind): An attacker lures a victim's browser to a malicious page, rebinds their domain to 127.0.0.1, and uses the browser as a proxy to invoke execute_sql as same-origin.

Root Cause

In src/mysql_mcp_server/server.py:

  1. SseServerTransport is constructed without security_settings — the SDK defaults enable_dns_rebinding_protection to False.
  2. The Starlette app has no CORS or TrustedHost middleware.
  3. All three routes (/, /sse, /messages/) are unauthenticated.
  4. The service binds to 0.0.0.0 by default.
  5. The sink is cursor.execute(query) with a fully attacker-controlled query.

Impact

  • Unauthenticated arbitrary SQL execution against the configured database
  • Full data exfiltration and modification
  • If the MySQL account holds FILE privilege: arbitrary file read (LOAD_FILE) and write (INTO OUTFILE) — potential RCE via webshell drop
  • Internet-wide scanning has identified 25 publicly reachable SSE instances of this project

Fix

Released in v0.4.2: DNS-rebinding protection is now enabled by passing TransportSecuritySettings(enable_dns_rebinding_protection=True) to SseServerTransport, and the documented recommended bind address is 127.0.0.1.

Credits

Discovered by Huanchen, SongWu (JHU), and BrookeYangRui (JHU).

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Risk Scores
Base Score
10.0

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.

Threat Intelligence
9.1

Active exploitation in the wild has been confirmed. Immediate patching or mitigation is required.

EPSS
0.39%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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