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CVE-2026-52870

MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks

Published: Jul 15, 2026Updated: Jul 17, 2026 Sources: CVE List NVDCWE-862
7.6HIGH
NVD MITRE
EPSS Score
0.2%
Top 85.4%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
Not available

Description

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). From 1.23.0 until 1.27.2, default handlers installed by server.experimental.enable_tasks() for tasks/list, tasks/get, tasks/result, and tasks/cancel operate only on task identifiers without recording the session that created each task, allowing any connected client to enumerate, read results from, consume messages for, or cancel other clients' tasks. This issue is fixed in version 1.27.2.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:NS:UC:HI:LA:L
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:LIntegrity
Low
A:LAvailability
Low
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Weaknesses

CWE-862

Affected Products

lfprojects
oss-projectaka mlflow, valkey, model context protocol servers, mcp servers
mcp python sdkMixed
AI / ML / notebook-mlops
modelcontextprotocol
oss-projectaka mcp, model context protocol
python-sdkMixed
AI / ML / ai-agent-tooling

Exploitability

Official Patch Available
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Initial Access
View detailed technique mapping

References

https://github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea80ff528a7fd9ca7a5e7
github.com
https://github.com/modelcontextprotocol/python-sdk/pull/2720
github.com
https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2
github.com
and 1 more references View all →

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