by Kastro
Paper/Archive/CVE-2025-34072

CVE-2025-34072

Anthropic Slack MCP Server — Anthropic Slack MCP Server Data Exfiltration via Link Unfurling

EPSS 0.4%public exploitCVSS 9.3
critical.is priorityof 100
45
CVSS 9.3 (CNA)9.3 / 10 × 3027.9Not in CISA KEV+300.0EPSS percentile 37.3.373 × 207.5Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
Slack MCP Serverall versions–CNA

Scores by source

VulnCheck (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:H
CISA ADPSSVCExploitation: poc · Automatable: no · Technical impact: partial

References

exploitembracethered.com/blog/posts/2025/security-advisory-anthropic-slack-mcp-server-data-leakagewriteupvulncheck.com/advisories/anthropic-slack-mcp-server-data-exfiltration