Microsoft SimpleChat up to 0.261.30 MCP Plugin Authorization /api/user/plugins _reject_non_admin_mcp_stdio improper authorization

Summaryinfo

A vulnerability was found in Microsoft SimpleChat up to 0.261.30. It has been classified as critical. This vulnerability affects the function _reject_non_admin_mcp_stdio of the file /api/user/plugins of the component MCP Plugin Authorization. This manipulation causes improper authorization. This vulnerability is tracked as CVE-2026-105797. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as critical was found in Microsoft SimpleChat up to 0.261.30. Affected by this vulnerability is the function _reject_non_admin_mcp_stdio of the file /api/user/plugins of the component MCP Plugin Authorization. The manipulation with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

SimpleChat is a secure AI conversation application with personal and group workspaces for document-grounded interactions. In versions 0.261.003 and 0.261.027, an authorization ordering flaw in POST /api/user/plugins allows an authenticated low-privileged user to omit the top-level MCP type so that _reject_non_admin_mcp_stdio skips inspection before the type is restored from metadata. The stored personal action can then reach McpPluginFactory.create_connector, and MCPStdioPlugin.connect starts the attacker-selected operating-system process under the application service identity when the action tool is invoked. Exploitation requires personal plugins to be enabled and governance to permit MCP actions, and it can expose or modify secrets and data available to the service or disrupt the service. This issue is fixed in version 0.261.031.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-105797 since 10/05/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/06/2026). The attack technique deployed by this issue is T1548.002 according to MITRE ATT&CK.

Upgrading to version 0.261.031 eliminates this vulnerability.

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Productinfo

Type

• Chat Software

Vendor

• Microsoft

Name

• SimpleChat

Version

• 0.261.0
• 0.261.1
• 0.261.2
• 0.261.3
• 0.261.4
• 0.261.5
• 0.261.6
• 0.261.7
• 0.261.8
• 0.261.9
• 0.261.10
• 0.261.11
• 0.261.12
• 0.261.13
• 0.261.14
• 0.261.15
• 0.261.16
• 0.261.17
• 0.261.18
• 0.261.19
• 0.261.20
• 0.261.21
• 0.261.22
• 0.261.23
• 0.261.24
• 0.261.25
• 0.261.26
• 0.261.27
• 0.261.28
• 0.261.29
• 0.261.30

License

• commercial

Website

• Vendor: https://www.microsoft.com/
• Product: https://github.com/microsoft/simplechat/

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