CVE-2026-52870MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks
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It affects modelcontextprotocol python-sdk and 1 other product. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 7.6 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L
- Weakness (CWE)
- CWE-862
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Analyzed
- Record last updated
- Jul 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
modelcontextprotocol python-sdk modelcontextprotocol:python_sdk (from the name) | from 1.23.0, < 1.27.2 | CNA record |
lfprojects mcp_python_sdk lfprojects:mcp_python_sdk | from 1.23.0 before 1.27.2 | NVD |
References
- https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp-rf83-w775x-refsource-confirm, vendor-advisory
- https://github.com/modelcontextprotocol/python-sdk/pull/2720x-refsource-misc, issue-tracking, patch
- https://github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea80ff528a7fd9ca7a5e7x-refsource-misc, patch
- https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2x-refsource-misc, release-notes
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.