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.
References (3)
Scores
CVSS v4
8.7
EPSS
0.0019
EPSS Percentile
41.2%
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
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
yes
Technical Impact
partial
Details
CWE
CWE-248
Status
published
Products (2)
modelcontextprotocol/python-sdk
< 1.9.4
pypi/mcp
0 - 1.9.4PyPI
Published
Jul 04, 2025
Tracked Since
Feb 18, 2026