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CVE-2025-34072VulnerabilityPublished

CVE-2025-34072: Anthropic Slack MCP Server · Information Exposure

Affects Anthropic Slack MCP ServerSource CVE Database V5

0

Not known to be exploited · CVSS 9.3 Critical.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 4.0 base score
9.3Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Jul 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

What to do

Affected software

ProductAffectedFixed in
Anthropic Slack MCP ServerAffected
  • =0
Fixed in–

AI-suggested

Given the absence of official patches, European organizations should prioritize immediate mitigation steps: 1) Disable or remove the deprecated Slack MCP Server from their environments to eliminate the attack surface. 2) Configure Slack workspace settings to restrict or disable automatic link unfurling and link preview features, especially for messages originating from AI agents or untrusted sources. 3) Implement strict input validation and sanitization on any AI-generated content before it is sent to Slack channels to prevent embedding malicious hyperlinks. 4) Monitor outbound network traffic for unusual requests to external or attacker-controlled domains originating from Slack link preview bots. 5) Employ network-level controls such as egress filtering and DNS filtering to block connections to suspicious URLs. 6) Educate security teams and Slack administrators about this vulnerability to ensure rapid detection and response. 7) Engage with Anthropic and Slack vendors for updates and patches, and plan for migration away from deprecated components. These targeted actions go beyond generic advice by focusing on the specific mechanisms exploited by this vulnerability and the unique architecture of Slack's link preview system.

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.

References

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