CVE-2025-27520: Critical Remote Code Execution Vulnerability in BentoML Python Library

Overview

The cybersecurity world is facing yet another critical vulnerability, this time in the form of a Remote Code Execution (RCE) flaw in the popular AI-serving Python Library, BentoML. This vulnerability, identified as CVE-2025-27520, is serious due to its potential for system compromise and data leakage, and the fact that it allows any unauthenticated user to execute arbitrary code on the server. System administrators, developers, and organizations utilizing BentoML, especially in its latest version v1.4.2, should be aware of this vulnerability and take immediate measures to mitigate the potential risks.

Vulnerability Summary

CVE ID: CVE-2025-27520
Severity: Critical (CVSS: 9.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Unauthenticated Remote Code Execution leading to potential system compromise and data leakage

Affected Products

Product | Affected Versions

BentoML | v1.4.2

How the Exploit Works

The exploit leverages insecure deserialization in BentoML’s ‘serde.py’ file. Deserialization is a process that converts data from a raw format into an object. If this process is insecure, an attacker can inject malicious code into serialized data. When this data is deserialized, it can lead to the execution of arbitrary code. In this case, an unauthenticated user could use this vulnerability to execute arbitrary commands on the server where BentoML is running.

Conceptual Example Code

Here is a conceptual example of how the vulnerability might be exploited:

POST /bentoml/api/serve HTTP/1.1
Host: target.example.com
Content-Type: application/python-serialize
{ "serialized_payload": "c__builtin__\neval\np0\n(S'import os; os.system(\"malicious_command\")'\np1\ntp2\nRp3\n." }

In this example, the attacker is sending a serialized Python object containing a malicious command (‘malicious_command’) within an HTTP POST request. When the server deserializes this payload, the command is executed on the server.

Mitigation and Patching

Given the high severity of this vulnerability, it’s crucial to apply the patch provided by the vendor immediately. BentoML version 1.4.3 includes a fix for this vulnerability. Organizations using vulnerable versions should upgrade to the latest version as soon as possible.
As a temporary measure, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can help prevent exploitation of this vulnerability. However, this should not be considered a long-term solution and is no substitute for patching the vulnerability.