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

> CVE-2025-34072: Anthropic Slack MCP Server Data Exfiltration via Link Unfurling. CVSS 9.3 (CVSS 4.0).

Canonical: https://rewindex.com/cve/CVE-2025-34072
Last updated: 2026-06-17T09:13:25Z

- Published: 2025-07-02 13:46 UTC · Updated: 2026-06-17 09:13 UTC · Assigner: VulnCheck
- CVSS: 9.3 (CVSS 4.0) · Severity: Critical
- EPSS: 0.43%, 37th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-20, CWE-200

## Description

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 data.

## Affected vendors and products

- Anthropic: Slack MCP Server

## Tracked companies

- [Anthropic](https://rewindex.com/company/anthropic.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2025-34072)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2025-34072)
- [https://embracethered.com/blog/posts/2025/security-advisory-anthropic-slack-mcp-server-data-leakage/](https://embracethered.com/blog/posts/2025/security-advisory-anthropic-slack-mcp-server-data-leakage/)
- [https://vulncheck.com/advisories/anthropic-slack-mcp-server-data-exfiltration](https://vulncheck.com/advisories/anthropic-slack-mcp-server-data-exfiltration)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2025-34072 · Markdown: https://rewindex.com/cve/CVE-2025-34072.md · JSON: https://rewindex.com/api/v1/cves/CVE-2025-34072 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:13:24.548Z