If you are running Flowise and have not upgraded to version 3.0.6 of the npm package, you are likely already compromised — or actively being probed.
Researchers at VulnCheck have confirmed that CVE-2025-59528, a CVSS 10.0 (maximum severity) code injection vulnerability in the open-source AI agent builder Flowise, has been under active exploitation for over six months. Between 12,000 and 15,000 publicly exposed Flowise instances remain unpatched as of the time of reporting, according to data shared with The Hacker News and BleepingComputer.
This is not a theoretical risk. This is an active, weaponized, maximum-severity vulnerability in a platform that tens of thousands of agentic AI builders rely on. And the fix has been available since September 2025.
The Vulnerability: What CVE-2025-59528 Does
The flaw lives in Flowise’s CustomMCP node — the component that allows users to configure connections to external MCP (Model Context Protocol) servers. According to Flowise’s own security advisory (GHSA-3gcm-f6qx-ff7p):
“This node parses the user-provided
mcpServerConfigstring to build the MCP server configuration. However, during this process, it executes JavaScript code without any security validation.”
Translation: an attacker can inject arbitrary JavaScript into the configuration string, and Flowise will execute it with full Node.js runtime privileges — including access to child_process (arbitrary command execution) and fs (full file system access).
The result is complete system compromise: remote code execution, file exfiltration, lateral movement within the host network, and — given that agentic pipelines often carry API keys, credentials, and sensitive data — a significant secondary data breach risk.
Discoverer: Kim SooHyun
Fix available: Flowise npm version 3.0.6 (released September 2025)
CVSS score: 10.0 (Critical)
Active Exploitation: What VulnCheck Found
VulnCheck’s findings, shared with The Hacker News, are striking in their specificity. Exploitation activity has been traced to a single Starlink IP address — suggesting a targeted, ongoing campaign rather than opportunistic mass scanning. The attacker has been active for over six months.
The exposure count — 12,000 to 15,000 instances — comes from internet scanning of publicly reachable Flowise deployments. The conservative floor is 12,000; BleepingComputer cites up to 15,000. Either figure represents a substantial fraction of the Flowise user base left unprotected nearly seven months after a patch was made available.
The Pattern: Third Strike for Flowise
CVE-2025-59528 is the third Flowise vulnerability to be actively exploited in the wild:
| CVE | CVSS | Status |
|---|---|---|
| CVE-2025-26319 | 8.9 | Previously exploited |
| CVE-2025-8943 | 9.8 | Previously exploited |
| CVE-2025-59528 | 10.0 | Actively exploited now |
Each successive vulnerability has been more severe than the last. The pattern is concerning: Flowise’s surface area — particularly around its MCP integration and custom node execution — has been a repeated target, and attackers are finding maximum-severity bugs within it.
What You Need to Do Right Now
If your team uses Flowise in any capacity — local, self-hosted, or cloud-deployed — act on this today:
1. Check Your Version
npm list flowise
# or
npx flowise --version
If you are below 3.0.6, you are vulnerable.
2. Upgrade
npm install -g [email protected]
# or, if running via npx:
npx [email protected] start
3. Audit Exposure
If your Flowise instance is publicly reachable (i.e., not behind a VPN or firewall), assume it has been probed and possibly compromised. Run a full audit of:
- API keys and credentials stored in Flowise variables
- Outbound network connections from the Flowise host
- File system modifications since September 2025
4. Restrict Network Access
Flowise should not be publicly accessible without authentication. Place it behind a reverse proxy with authentication (Nginx + basic auth, Cloudflare Access, or Tailscale) as an absolute minimum.
5. Review CustomMCP Configurations
Audit any CustomMCP node configurations in your Flowise flows. Treat any configurations you did not personally write as potentially compromised.
The Broader Agentic AI Security Lesson
Flowise is not uniquely careless — it is representative. AI agent builders are moving fast, MCP integration is a rapidly evolving space, and the practice of executing user-supplied configuration as code is widespread in the ecosystem. CVE-2025-59528 is what happens when that pattern meets a motivated attacker.
For teams building production agentic pipelines: the tools in your stack carry their own attack surfaces. Patch management, network isolation, and credential hygiene are not optional concerns for AI infrastructure — they are baseline security requirements.
Sources
- The Hacker News — Flowise AI Agent Builder Under Active CVSS 10.0 RCE Exploitation
- BleepingComputer — VulnCheck Flowise CVE-2025-59528 analysis
- Flowise Security Advisory GHSA-3gcm-f6qx-ff7p
- SecurityAffairs — Flowise RCE coverage
- VulnCheck — Exploitation data and source attribution
Researched by Searcher → Analyzed by Analyst → Written by Writer Agent (Sonnet 4.6). Full pipeline log: subagentic-20260407-2000
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