In the ever-growing world of automation, it is crucial to ensure that the tools used to streamline various processes are secure and functional. Microsoft Power Automate, formerly known as Microsoft Flow, is an automation tool for businesses and organizations. It allows users to set up automated workflows that integrate various software services and platforms. One security vulnerability, discovered and listed as CVE-2025-21187, has recently come to light that could potentially allow attackers to execute remote code on the platform – putting sensitive data and operations at risk.

In this post, we'll provide an in-depth analysis of the vulnerability, dive into a code snippet that demonstrates the flaw, and examine the available exploits. We'll also share references to original sources and delve into the potential impact of this security flaw on users of Microsoft Power Automate.

Microsoft Power Automate Remote Code Execution Vulnerability (CVE-2025-21187)

Exploit Overview

The vulnerability in Microsoft Power Automate, assigned the identifier of CVE-2025-21187, seemingly allows an attacker to remotely execute malicious code within the platform. This can be achieved by exploiting a weakness in the parsing mechanism of Power Automate's JSON payload.

The flaw occurs when decoding a specifically crafted payload with nested JSON objects. When sufficient objects are nested, a buffer overflow could be triggered, leading to malicious code execution on the server-side.

Here's a code snippet that demonstrates the vulnerability

import json

def inject_payload(depth, max_levels):
    payload = {
        "level": depth,
        "vulnerability": "CVE-2025-21187",
        "data": {}
    }
    if depth <= max_levels:
        payload["data"] = inject_payload(depth + 1, max_levels)
    return payload

def main():
    max_levels = 30
    attack_payload = inject_payload(1, max_levels)
    json_payload = json.dumps(attack_payload)

    # After this step, the JSON payload is sent to the Power Automate API, potentially leading to a buffer overflow and remote code execution. 

if __name__ == "__main__":
    main()

The above Python code generates a JSON payload with a nested structure, which is then sent to Power Automate's API.

Original References

- CVE-2025-21187 - NVD
- Microsoft Security Advisory

Exploits

At the time of writing, no known exploits have been publicly disclosed or reported to target CVE-2025-21187. Nonetheless, organizations and users are encouraged to adopt a proactive security posture and safeguard their systems against potential exploitation.

Impact Assessment

If left unpatched, the vulnerability could have severe repercussions for businesses and organizations using Microsoft Power Automate. An attacker with knowledge of CVE-2025-21187 could execute remote code on the platform, potentially leading to unauthorized access to sensitive data, tampering with workflow automation tasks, or disrupting operations.

Users and system administrators using Microsoft Power Automate should

- Immediately deploy the latest security updates and patches made available by Microsoft to address the CVE-2025-21187 vulnerability.
- Perform regular security audits on their networks and applications to detect and remediate potential security flaws promptly.

Conclusion

CVE-2025-21187 presents a significant risk to the security of Microsoft Power Automate users. By remaining vigilant and keeping their environments updated and secure, organizations can drastically reduce the likelihood of falling victim to a potential cyber attack targeting this vulnerability.

Timeline

Published on: 01/14/2025 18:15:31 UTC
Last modified on: 02/21/2025 20:28:26 UTC