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

> Attackers can exfiltrate sensitive data via crafted links in AI agent messages, triggering Slack's link preview bots to send data to attacker-controlled servers.

- **Severity:** Critical 9.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Jul 2025
- **Updated:** 2 Jul 2025
- **Also known as:** GHSA-gmx5-crwh-6vxg

## What is CVE-2025-34072?

CVE-2025-34072 is a critical vulnerability in Anthropic Slack MCP Server, published on 2 Jul 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2025-34072?


## How do I fix CVE-2025-34072?

No fix has been published for CVE-2025-34072 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-34072 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-34072 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-34072 and fix it if it is affected.

What it is: CVE-2025-34072 is a critical vulnerability in Anthropic Slack MCP Server, published on 2 Jul 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-34072 exists.

Affected product: Anthropic Slack MCP Server. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-34072/ (Markdown: https://insights.sbomify.com/CVE-2025-34072/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-34072
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-34072
- OSV: https://osv.dev/vulnerability/CVE-2025-34072

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-34072/
Summaries are generated and may contain mistakes; the official description above is the record.