Vulnerability · Published Jul 15, 2026 · Assigned by GitHub_M

CVE-2026-52870MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks

High 7.6

In plain English

A high-severity missing authorization in python-sdk from modelcontextprotocol. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 33% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.6High

Exploit odds (30 days)0.4%top 66.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	mcp	1.27.2	GHSA-hvrp-rf83-w775
PyPI	mcp	1.27.2	PYSEC-2026-3481

Affected products (as reported)

Vendor	Product	Versions
modelcontextprotocol	python-sdk	>= 1.23.0, < 1.27.2

Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L

References

https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp-rf83-w775 x_refsource_CONFIRM
https://github.com/modelcontextprotocol/python-sdk/pull/2720 x_refsource_MISC
https://github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea80ff528a7fd9ca7a5e7 x_refsource_MISC
https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2 x_refsource_MISC