CVE-2025-34072 – Anthropic Slack MCP Server Data Exfiltration via Link Unfurling

https://notcve.org/view.php?id=CVE-2025-34072

02 Jul 2025 — A data exfiltration vulnerability exists in Anthropic’s deprecated Slack Model Context Protocol (MCP) Server via automatic link unfurling. When an AI agent using the Slack MCP Server processes untrusted data, it can be manipulated to generate messages containing attacker-crafted hyperlinks embedding sensitive data. Slack’s link preview bots (e.g., Slack-LinkExpanding, Slackbot, Slack-ImgProxy) will then issue outbound requests to the attacker-controlled URL, resulting in zero-click exfiltration of private d... • https://embracethered.com/blog/posts/2025/security-advisory-anthropic-slack-mcp-server-data-leakage • CWE-20: Improper Input Validation CWE-200: Exposure of Sensitive Information to an Unauthorized Actor •