Hackers are exploiting a maximum-severity vulnerability, tracked as CVE-2025-59528, in the open-source platform Flowise for building custom LLM apps and agentic systems to execute arbitrary code. The flaw allows injecting JavaScript code without any security checks and was publicly disclosed last September, with the warning that successful exploitation leads to command execution and file system access. The problem is with the Flowise CustomMCP node allowing configuration settings to connect to an external Model Context Protocol (MCP) server and unsafely evaluating the mcpServerConfig input from the user. During this process, it can execute JavaScript without first validating its safety. The developer addressed the issue in Flowise version 3.0.6. The latest current version is 3.1.1, released two weeks ago. Flowise is an open-source, low-code platform for building AI agents and LLM-based workflows. It provides a drag-and-drop interface that lets users connect components into pipelines powering chatbots, automation, and AI systems. It is used by a broad range of users, including developers working in AI prototyping, non-technical users working with no-code toolsets, and companies that operate customer support chatbots and knowledge-based assistants. Caitlin Condon, security researcher at vulnerability intelligence company VulnCheck, announced on LinkedIn that exploitation of CVE-2025-59528 has been detected by their Canary network. “Early this morning, VulnCheck's Canary networ...
Max severity Flowise RCE vulnerability now exploited in attacks
BleepingComputer
·Bill Toulas
·Published Apr 7, 2026
·Updated
Affected Software
2 affected components
Flowise Flowise<3.0.6
Flowise CustomMCP node<3.0.6
Frequently Asked Questions
1
What is the main topic of this article?
The article discusses the exploitation of a critical remote code execution vulnerability in the Flowise software.
2
What vulnerability is being exploited according to the article?
The vulnerability tracked as CVE-2025-59528 is being exploited by hackers.
3
What are the security implications of this Flowise vulnerability?
The vulnerability allows attackers to execute arbitrary code by injecting JavaScript code without security checks.
4
Which platform is affected by this vulnerability?
The affected platform is Flowise, an open-source tool for building custom LLM applications.
5
When was the Flowise vulnerability publicly disclosed?
The vulnerability was publicly disclosed in late 2025.