CVE-2026-59971: MySQL MCP Server: Missing Origin/Host Validation in SSE Transport Enables Unauthenticated SQL Execution (DNS Rebinding / Direct Exposure)

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.4%, percentile 35: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 35% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes mysql-mcp-server (PyPI) < 0.4.2, fixed in 0.4.2. Check your lockfile, including transitive dependencies.

What it is

MySQL MCP Server is a Model Context Protocol server that enables secure interaction with MySQL databases. Prior to 0.4.2, setting MCPTRANSPORT=sse causes src/mysqlmcpserver/server.py to construct SseServerTransport without securitysettings or enablednsrebindingprotection, while the Starlette routes /, /sse, and /messages/ have no authentication and the service binds to 0.0.0.0 by default. A network attacker can directly reach executesql, or can use DNS rebinding to make a victim's browser relay same-origin requests to a locally bound service, and supply a query that reaches cursor.execute(query). This allows unauthenticated disclosure and modification of the configured database; when the MySQL account has FILE privileges, the same access can read or write server files and may enable code execution. The default stdio transport is not affected. This issue is fixed in 0.4.2.

From the GitHub advisory

Summary

In SSE/HTTP transport mode, mysqlmcpserver constructs SseServerTransport without passing securitysettings. 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: MCPTRANSPORT=sse. The default stdio mode is not affected.

Attack Scenarios

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

Weakness type: CWE-306, CWE-346.

Product: mysql-mcp-server (PyPI) · Assigned by: GitHub_M · Published: 2026-09-15

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.42% probability of exploitation activity in the next 30 days; percentile 35.

Timeline

• 2026-09-11 — GitHub-reviewed advisory GHSA-rqfv-2mw9-78g2 published (critical)
• 2026-09-15 — CVE record last updated
• 2026-09-15 — CVE record published by GitHub_M

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-rqfv-2mw9-78g2 github.com
2. CVE.org record CVE-2026-59971 cve.org
3. NVD entry CVE-2026-59971 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com

Critical PyPI advisories · Today’s Security Digest