High severityNVD Advisory· Published Jul 15, 2026· Updated Jul 16, 2026
MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks
CVE-2026-52870
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
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
mcpPyPI | >= 1.23.0, < 1.27.2 | 1.27.2 |
Affected products
4- Range: 1.23.0 - 1.27.2
- osv-coords3 versions
< 1.93.0-r0+ 2 more
- (no CPE)range: < 1.93.0-r0
- (no CPE)range: < 1.172.0-r1
- (no CPE)range: < 1.172.0-r1
Patches
Vulnerability mechanics
References
6- github.com/advisories/GHSA-hvrp-rf83-w775ghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-52870ghsaADVISORY
- github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea80ff528a7fd9ca7a5e7ghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/python-sdk/pull/2720ghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2ghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp-rf83-w775ghsax_refsource_CONFIRMWEB
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