Improper Task Handling in Python SDK by Model Context Protocol
CVE-2026-52870

7.6HIGH

Key Information:

Vendor

Modelcontextprotocol

Status
Python-sdk
Vendor
CVE Published:
15 July 2026

What is CVE-2026-52870?

The MCP Python SDK (mcp on PyPI), versions 1.23.0 to 1.27.2, contains an improper access control vulnerability. The default handlers used when enabling tasks through server.experimental.enable_tasks() allow interconnected clients to handle task identifiers without safeguarding the originating session. This leads to unauthorized access, allowing clients to enumerate, read, cancel, or consume messages pertaining to tasks initiated by other users. This issue has been resolved in the subsequent version 1.27.2.

Affected Version(s)

python-sdk >= 1.23.0, < 1.27.2

References

https://github.com/modelcontextprotocol/python-sdk/securi...
x_refsource_CONFIRM
https://github.com/modelcontextprotocol/python-sdk/pull/2720
x_refsource_MISC
https://github.com/modelcontextprotocol/python-sdk/commit...
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CVSS V3.1

Score:
7.6
Severity:
HIGH
Confidentiality:
High
Integrity:
Low
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.