CVE-2026-52870: CWE-862: Missing Authorization in modelcontextprotocol python-sdk
The MCP Python SDK (modelcontextprotocol python-sdk) versions from 1.23.0 up to but not including 1.27.2 contain a missing authorization vulnerability. Default handlers for task-related operations do not associate tasks with the creating session, allowing any connected client to access or manipulate other clients' tasks. This issue allows enumeration, reading results, consuming messages, or canceling tasks belonging to other clients. The vulnerability is fixed starting from version 1.27.2.
AI Analysis
Technical Summary
CVE-2026-52870 is a missing authorization vulnerability (CWE-862) in the MCP Python SDK (modelcontextprotocol python-sdk). Between versions 1.23.0 and 1.27.2, the default handlers installed by server.experimental.enable_tasks() for endpoints tasks/list, tasks/get, tasks/result, and tasks/cancel operate solely on task identifiers without tracking the session that created each task. This flaw permits any connected client to enumerate, read results from, consume messages for, or cancel tasks created by other clients. The vulnerability is resolved in version 1.27.2.
Potential Impact
An attacker with at least low privileges (PR:L) and network access (AV:N) can exploit this vulnerability to access or interfere with tasks belonging to other clients. This leads to confidentiality impact (C:H) by exposing task results, integrity impact (I:L) by potentially consuming messages, and availability impact (A:L) by allowing cancellation of other clients' tasks. The vulnerability does not require user interaction and has a high severity score of 7.6.
Mitigation Recommendations
Upgrade the MCP Python SDK to version 1.27.2 or later, where this missing authorization issue is fixed. No other official remediation or temporary fixes are documented. Until upgrading, restrict access to the MCP server to trusted clients to reduce risk.
CVE-2026-52870: CWE-862: Missing Authorization in modelcontextprotocol python-sdk
Description
The MCP Python SDK (modelcontextprotocol python-sdk) versions from 1.23.0 up to but not including 1.27.2 contain a missing authorization vulnerability. Default handlers for task-related operations do not associate tasks with the creating session, allowing any connected client to access or manipulate other clients' tasks. This issue allows enumeration, reading results, consuming messages, or canceling tasks belonging to other clients. The vulnerability is fixed starting from version 1.27.2.
CVSS v3.1
Score 7.6high
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-52870 is a missing authorization vulnerability (CWE-862) in the MCP Python SDK (modelcontextprotocol python-sdk). Between versions 1.23.0 and 1.27.2, the default handlers installed by server.experimental.enable_tasks() for endpoints tasks/list, tasks/get, tasks/result, and tasks/cancel operate solely on task identifiers without tracking the session that created each task. This flaw permits any connected client to enumerate, read results from, consume messages for, or cancel tasks created by other clients. The vulnerability is resolved in version 1.27.2.
Potential Impact
An attacker with at least low privileges (PR:L) and network access (AV:N) can exploit this vulnerability to access or interfere with tasks belonging to other clients. This leads to confidentiality impact (C:H) by exposing task results, integrity impact (I:L) by potentially consuming messages, and availability impact (A:L) by allowing cancellation of other clients' tasks. The vulnerability does not require user interaction and has a high severity score of 7.6.
Mitigation Recommendations
Upgrade the MCP Python SDK to version 1.27.2 or later, where this missing authorization issue is fixed. No other official remediation or temporary fixes are documented. Until upgrading, restrict access to the MCP server to trusted clients to reduce risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-08T21:44:27.364Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a57eb0d68715ace4363c934
Added to database: 07/15/2026, 20:18:21 UTC
Last enriched: 07/15/2026, 20:32:28 UTC
Last updated: 07/15/2026, 21:37:56 UTC
Views: 5
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