Threat Library

The fast-mcp-telegram MCP server fails to sanitize Bearer tokens used for session file lookup, allowing a remote attacker to use path traversal sequences to authenticate as the default legacy Telegram session. This effectively bypasses the server's multi-user session isolation, letting an unauthenticated or low-privilege remote client impersonate the primary account owner and access their Telegram session and MCP tools.

A critical flaw in the widely used mcp-remote OAuth proxy let malicious MCP servers achieve remote code execution on connecting developer machines, turning a routine agent connection into full host compromise. The package had hundreds of thousands of downloads before patching.