Overview
In this blog post, we delve into a high-severity vulnerability, CVE-2025-50460, that exists in the ms-swift project version 3.3.0. The vulnerability is classified as a Remote Code Execution (RCE), one of the most dangerous forms of cybersecurity flaws. By exploiting this vulnerability, an attacker can compromise a system, leading to potential data leakage or full system control. This vulnerability is particularly concerning because it can be exploited remotely, which means an attacker does not need physical access to the vulnerable system.
Vulnerability Summary
CVE ID: CVE-2025-50460
Severity: Critical (9.8 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage
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Product | Affected Versions
ms-swift | 3.3.0
How the Exploit Works
The vulnerability resides in the tests/run.py file of the ms-swift project. Specifically, it has to do with the unsafe deserialization of a YAML configuration file using yaml.load() from the PyYAML library. If an attacker can control the content of the YAML configuration file passed to the –run_config parameter, they can execute arbitrary code during deserialization. The vulnerability is triggered when a malicious YAML file is loaded, which allows the execution of arbitrary Python commands such as os.system(), leading to full system compromise.
Conceptual Example Code
Below is a conceptual example of the malicious payload that could be used to exploit this vulnerability:
# Load malicious YAML file
with open("malicious.yaml", "r") as file:
data = yaml.load(file)
# Malicious YAML content
"""
!!python/object/apply:os.system ['cat /etc/passwd > /tmp/passwords.txt']
"""In this example, the malicious YAML file contains a Python os.system() command that exports the content of the /etc/passwd file (which contains user account details) to a file named passwords.txt in the /tmp directory. This is just a simple example; an attacker could execute any command that the system permissions allow.
Mitigation Guidance
The best way to mitigate this vulnerability is to upgrade the PyYAML library to version 5.4 or higher and replace yaml.load() with yaml.safe_load() in the tests/run.py script. This will prevent arbitrary code execution during YAML deserialization. As a temporary measure until the patch can be applied, it is recommended to use a Web Application Firewall (WAF) or intrusion detection system (IDS) to detect and block any attempts to exploit this vulnerability.