MCPA-2026-0032
highauth-missingCVSS 7.6
MCP Python SDK experimental task handlers expose other clients’ tasks (CVE-2026-52870)
The MCP Python SDK (PyPI: mcp) 1.23.0 through 1.27.1: the default request handlers installed by the experimental tasks feature (server.experimental.enable_tasks()) did not check which session created a task before acting on it. On a server with more than one connected client, any client could observe, read results from, and cancel tasks belonging to other clients. Fixed in 1.27.2.
Affected packages
| Ecosystem | Package | Affected versions |
|---|---|---|
| pypi | mcp | >= 1.23.0, < 1.27.2 |
Identifiers
CVE-2026-52870GHSA-hvrp-rf83-w775CWE-862
References
- advisory https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp-rf83-w775
- web https://nvd.nist.gov/vuln/detail/CVE-2026-52870
- fix https://github.com/modelcontextprotocol/python-sdk/pull/2720
- web https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2
Timeline
- Published: 2026-07-16