Critical Langflow RCE Flaw Exploited to Hack AI App Servers

The U.S. Cybersecurity & Infrastructure Security Agency (CISA) has issued a warning about a critical remote code execution (RCE) vulnerability in the open-source visual programming tool, Langflow. This flaw, tracked as CVE-2025-3248, has been actively exploited by attackers, and organizations are urged to apply security updates and mitigations as soon as possible.

Langflow is widely used by AI developers, researchers, and startups for prototyping chatbots, data pipelines, agent systems, and AI applications. The tool provides a drag-and-drop interface to create, test, and deploy AI agents or pipelines without writing full backend code. With its nearly 60k stars and 6.3k forks on GitHub, Langflow has become an essential tool in the AI development ecosystem.

The Vulnerability

The Langflow RCE flaw (CVE-2025-3248) allows any attacker on the internet to take full control of vulnerable Langflow servers by exploiting an API endpoint flaw. The vulnerability is critical, unauthenticated, and can be exploited without requiring any authentication.

In vulnerable versions, Langflow exposes an endpoint (/api/v1/validate/code) designed to validate user-submitted code. However, this endpoint does not safely sandbox or sanitize the input, allowing an attacker to send malicious code to that endpoint and have it executed directly on the server. This means that even if an attacker is not authenticated to the server, they can still inject malicious code and gain control over the server.

The Impact

The Langflow RCE flaw has significant implications for organizations that rely on this tool for their AI development and deployment needs. By exploiting this vulnerability, attackers can potentially gain access to sensitive data, disrupt operations, or even use the compromised servers as a pivot point for further attacks.

The Fix

The vulnerability was fixed in version 1.3.0, released on April 1, 2025. However, this patch only added authentication for the vulnerable endpoint, involving no sandboxing or hardening. The latest Langflow version, 1.4.0, was released earlier today and contains a long list of fixes.

Recommendations

CISA has recommended that organizations upgrade to version 1.3.0 or later to mitigate the risks associated with this vulnerability. However, for those who cannot upgrade immediately, CISA recommends restricting network access to Langflow by putting it behind a firewall, authenticated reverse proxy, or VPN.

Additionally, direct internet exposure is discouraged, and users are advised to limit their exposure to vulnerable instances until they can be upgraded. CISA has given federal agencies until May 26, 2025, to apply the security update or mitigations or stop using the software.

The Root Cause

The Langflow RCE flaw is a critical example of the importance of secure coding practices and the need for robust security measures. According to Horizon3 researchers, the tool's design has poor privilege separation, no sandbox, and a history of RCEs "by design" stemming from its nature and intended functionality.

CVE-2025-3248 is the first truly unauthenticated RCE flaw in Langflow, and given its active exploitation status, immediate action is required. Organizations must take this vulnerability seriously and prioritize their security posture to prevent potential attacks.