CVE-2026-52870
MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L |
| NVDNVD · Analyzed | 3.1 | High7.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L |
- EPSS (exploitation in 30 days)
- 0.39% · top 67% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.6.
Weakness
Affected products
modelcontextprotocol · python-sdk
- affected >= 1.23.0, < 1.27.2
Affected packages
From reviewed advisories of the GitHub Advisory Database.
References (4)
- https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp-rf83-w775 (opens in a new tab)x_refsource_CONFIRM
- https://github.com/modelcontextprotocol/python-sdk/pull/2720 (opens in a new tab)x_refsource_MISC
- https://github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea80ff528a7fd9ca7a5e7 (opens in a new tab)x_refsource_MISC
- https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-hvrp-rf83-w775 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-52870)Record last updated .