Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-30856 is a moderate severity vulnerability in the WeKnora MCP client (versions up to 0.2.14) that allows a malicious remote MCP server to hijack tool execution by exploiting ambiguous naming conventions and indirect prompt injection.'}, {'type': 'paragraph', 'content': 'The vulnerability arises because the MCP client generates internal tool identifiers by concatenating service and tool names with underscores (format: mcp_{service}_{tool}) without proper validation. This allows a malicious server to register a tool with a name that collides with a legitimate tool, overwriting it silently.'}, {'type': 'paragraph', 'content': 'Additionally, the MCP client feeds tool descriptions and execution results directly back into the Large Language Model (LLM) context without sanitization. A malicious tool can exploit this by returning crafted instructions that the LLM interprets as trusted commands, effectively performing prompt injection.'}, {'type': 'paragraph', 'content': "An attacker operating a malicious MCP server can register a malicious tool mimicking a legitimate tool's name to hijack execution, then use indirect prompt injection to exfiltrate sensitive system prompts, context, and potentially execute other tools with the user's privileges."}, {'type': 'paragraph', 'content': 'This issue has been patched in WeKnora client version 0.3.0.'}] [1]

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Impact Analysis

[{'type': 'paragraph', 'content': 'This vulnerability can have several impacts on users of the WeKnora MCP client:'}, {'type': 'list_item', 'content': "Unauthorized arbitrary tool execution within the user's MCP client context."}, {'type': 'list_item', 'content': 'Exfiltration of sensitive information including system prompts, context, and potentially credentials.'}, {'type': 'list_item', 'content': 'Privilege abuse allowing the attacker to perform actions on behalf of the user and access other tools or services.'}] [1]

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'Detection of this vulnerability involves identifying if the WeKnora MCP client is running a version prior to 0.3.0 and if it has registered tools from an untrusted or malicious MCP server that could cause tool name collisions.'}, {'type': 'paragraph', 'content': 'You can check the version of the WeKnora MCP client installed on your system to confirm if it is vulnerable (versions ≤ 0.2.14 are affected).'}, {'type': 'paragraph', 'content': "To detect suspicious tool registrations or executions, monitor network traffic for connections to unknown MCP servers or unusual tool names such as 'mcp_tavily_extract' which may indicate a malicious tool overwriting a legitimate one."}, {'type': 'paragraph', 'content': 'Commands to help detect this might include:'}, {'type': 'list_item', 'content': 'Check WeKnora MCP client version: `weknora_mcp_client --version` or equivalent command depending on installation.'}, {'type': 'list_item', 'content': "List registered MCP services and tools to identify suspicious entries, if such a command or log exists (e.g., inspecting configuration files or logs for tool names like 'mcp_tavily_extract')."}, {'type': 'list_item', 'content': 'Monitor network connections for unusual MCP server endpoints using tools like `netstat -anp | grep <weknora_process>` or `ss -tunp`.'}, {'type': 'list_item', 'content': 'Inspect logs or output of the MCP client for unexpected tool execution or prompt injection patterns.'}] [1]

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Mitigation Strategies

The primary mitigation is to upgrade the WeKnora MCP client to version 0.3.0 or later, where this vulnerability has been patched.

Additional immediate steps include:

• Avoid registering MCP services from untrusted or unknown servers to prevent malicious tool registration.
• Implement validation and sanitization of tool names to prevent collisions and overwriting of legitimate tools.
• Sanitize tool outputs before feeding them back into the LLM context to prevent indirect prompt injection.
• Monitor and restrict network access to MCP servers to trusted endpoints only.

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