CVE-2025-53366 | BDVDB-2026-284864 Detail

modelcontextprotocolpython-sdk

Description#

The MCP Python SDK, called `mcp` on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.9.4, a validation error in the MCP SDK can cause an unhandled exception when processing malformed requests, resulting in service unavailability (500 errors) until manually restarted. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures. Version 1.9.4 contains a patch for the issue.

Impact#

Per CVSS v4.0: confidentiality impact none, integrity impact none, availability impact high. Attack vector: network.

Weaknesses#

CWE-248 Uncaught Exception

References#

Exploit#

No public exploit known

History#

Version 12025-07-04Record published in the CVE List.
Version 22025-07-08Most recent update recorded in the CVE List.

Published

Published: 2025-07-04
Last modified: 2025-07-08

Vendor information

Vendor: modelcontextprotocol
Product: python-sdk

All modelcontextprotocol vulnerabilities

Score

8.7 High

EPSS

9.7%, Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 95.6.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Not classified

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
< 1.9.4
Fixed
Not stated

Scoring System

CVSS v4.0

8.7 High

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Metric breakdown
Attack Vector	Network
Attack Complexity	Low
Attack Requirements	None
Privileges Required	None
User Interaction	None
Vulnerable System Confidentiality	None
Vulnerable System Integrity	None
Vulnerable System Availability	High
Subsequent System Confidentiality	None
Subsequent System Integrity	None
Subsequent System Availability	None

CVSS v3.1

Not available

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).