Auth bypass in Lfprojects Mcp Python Sdk
CVE-2026-52870
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.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L.
EPSS exploit prediction
EPSS: 0.004 (30.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 31st percentile — 30.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Lfprojects Mcp Python Sdk
- Modelcontextprotocol Python-Sdk — versions >= 1.23.0, < 1.27.2
Weakness classification (CWE)
References
- github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea80ff528a… (Patch)
- github.com/modelcontextprotocol/python-sdk/pull/2720 (Patch, Issue Tracking)
- github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2 (Release Notes)
- github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp-rf83-w… (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-52870?
- CVE-2026-52870 is a high-severity vulnerability in Lfprojects Mcp Python Sdk, classified under Missing Authorization. CVSS score: 7.6/10. Published 2026-07-15.
- How severe is CVE-2026-52870?
- High severity. CVSS v3 base score is 7.6 out of 10.