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TI-2025-24240 Aliases CVE-2025-34072GHSA-gmx5-crwh-6vxg

Anthropic Slack MCP Server Data Exfiltration via Link Unfurling

Priority HIGH 73CWE-20Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Information disclosure
Confidentiality · integrity · availability
High · None · None
Fix status
No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-200.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.0043 37th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by the CNA
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
anthropicsSlack MCP Serverall versions—No fix listedCNA
  • Slack MCP Server Vendoranthropics Affected all versions Fixed in — No fix listed CNA

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-34072
  2. 2026-10-03 Alias added: GHSA-gmx5-crwh-6vxg

References

Exploit 1

  • TI-2026-79288 Out-of-bounds write in Google Brotli decoder KEVCVSS 4.0CRITICAL 9.2
  • TI-2026-00421 MCP TypeScript SDK UriTemplate Exploded Array Pattern ReDoS CVSS 4.0HIGH 8.7
  • TI-2025-40558 Claude Code Command Validation Bypass Allows Arbitrary Code Execution CVSS 4.0HIGH 8.7
  • TI-2025-36683 Claude Code vulnerable to arbitrary code execution caused by maliciously configured git email CVSS 4.0HIGH 8.7
  • TI-2025-32918 Claude Code IDE extensions allow websocket connections from arbitrary origins CVSS 4.0HIGH 8.8
  • TI-2025-37066 Claude Code's startup trust dialog could lead to Command Execution attack CVSS 4.0HIGH 8.7
See all 46 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences