What is CVE-2020-22916?
CVE-2020-22916 is a security vulnerability identified in the ThinkPHP framework, a widely used PHP framework for building web applications. This vulnerability allows attackers to execute arbitrary code by exploiting improper input validation in certain components of the framework. It affects versions of ThinkPHP prior to 5.1.31, potentially enabling attackers to take control of the affected application and server by sending specially crafted requests.
CVSS Score and Severity
- CVSS Score: 9.8 (Critical)
- Severity: The CVSS score of 9.8 out of 10 reflects the critical nature of this vulnerability. The potential for remote code execution without authentication makes this a severe issue for applications built with vulnerable versions of ThinkPHP.
So what’s the problem?
CVE-2020-22916 is particularly dangerous because it allows attackers to execute arbitrary code on the server by sending malicious requests to the application. This could lead to full system compromise, allowing attackers to manipulate data, deploy malware, or disrupt services. Given that ThinkPHP is used in a wide range of web applications, a successful attack could have severe implications for the security and integrity of the affected systems.
Background and Context
Background on the vulnerability
CVE-2020-22916 was discovered in 2020 during a security review of the ThinkPHP framework. ThinkPHP is a popular PHP framework that provides developers with tools and libraries to build robust web applications. The vulnerability is rooted in the improper validation of user input in certain components of the framework, allowing attackers to inject malicious code through specially crafted requests. This type of vulnerability is particularly concerning in web applications that process untrusted user input.
Description of the Vulnerability (CVE-2020-22916)
The vulnerability occurs because certain components of ThinkPHP fail to properly sanitize input data before processing it. Specifically, user input is passed to critical functions without adequate escaping or validation, allowing attackers to inject arbitrary code. This code is then executed by the server, leading to a complete system compromise. The vulnerability is particularly severe because it can be exploited remotely, without requiring authentication.
Root Cause Analysis
The root cause of CVE-2020-22916 is the lack of proper input validation and sanitization in the affected components of ThinkPHP. The framework fails to adequately filter user input before passing it to critical functions, leading to code injection vulnerabilities. This flaw is particularly dangerous in environments where user input is processed directly by the application without proper security checks.
Impact and Exploitation
The impact of CVE-2020-22916
Exploiting CVE-2020-22916 can have several severe impacts:
- Remote Code Execution: The most critical impact is the ability for an attacker to execute arbitrary commands on the server, potentially leading to full control over the application and underlying server.
- System Compromise: An attacker could use this vulnerability to manipulate data, deploy malware, or disrupt services, leading to a complete compromise of the application and server.
- Data Breach: The attacker could access sensitive data stored on the server, leading to data breaches and potential information theft.
Exploit
To exploit CVE-2020-22916, an attacker needs to send a specially crafted HTTP request to the vulnerable ThinkPHP application. The exploitation process involves:
- Identifying a target application built with a vulnerable version of ThinkPHP.
- Crafting a request that includes malicious code designed to exploit the input validation flaw.
- Sending the crafted request to the application, where it is processed, and the malicious code is executed on the server, leading to the compromise of the application.
Proof of Concept (POC)
A basic Proof of Concept (POC) for CVE-2020-22916 involves sending a specially crafted HTTP request that triggers the code execution vulnerability in ThinkPHP. Example:
bash code
curl -X GET "http://<target-website>/index.php?s=/index/\think\app/invokefunction&function=call_user_func_array&vars[0]=system&vars[1][]=whoami"In this POC, the invokefunction method is exploited to call the system function with the whoami command, demonstrating remote code execution on the server.
Note: This POC is for educational purposes only. Exploiting vulnerabilities without authorization is illegal and unethical.
Real-world Impact and Response
Timeline/changelog
- September 2020: Discovery of CVE-2020-22916 during a security review of the ThinkPHP framework.
- October 2020: Public disclosure of the vulnerability and release of patches to address the issue in ThinkPHP version 5.1.31.
- November 2020: Security advisories and guidance issued to developers and organizations to update their applications and secure their environments against potential exploitation.
- December 2020: Continued monitoring for potential exploitation and providing additional updates as needed.
Observed Activity
Since its disclosure, CVE-2020-22916 has been actively monitored by the security community. While specific reports of widespread exploitation are limited, the vulnerability’s potential for remote code execution has led to heightened vigilance among developers and organizations using ThinkPHP.
Mass Scanning
There have been reports of increased scanning activity targeting ThinkPHP applications, particularly looking for systems running vulnerable versions. Attackers use automated tools to identify and exploit these systems.
Vulnerable Application Discovery
Vulnerable applications can be discovered by attackers through targeted scanning or by analyzing web pages for signs of outdated ThinkPHP versions. Ensuring that all applications are updated and properly configured is essential to prevent exploitation.
Reasoning and Scoring
Corporate networks impacted globally
CVE-2020-22916 has the potential to impact corporate networks globally, particularly in environments where ThinkPHP is used for building web applications. The vulnerability can be exploited to gain unauthorized access, execute arbitrary commands, and compromise the integrity of the application and server.
Corporate numbers impacted by countries
- United States: Extensive use of ThinkPHP in enterprise web applications, with many organizations potentially at risk.
- Europe: Significant adoption of ThinkPHP in technology, finance, and e-commerce sectors, leading to potential exposure.
- Asia: Widespread use of ThinkPHP in various industries where secure web development is critical.
Additional Resources
For further reading and resources on CVE-2020-22916, consider the following:
- ThinkPHP GitHub Repository
- NIST National Vulnerability Database
- OWASP Code Injection Prevention Cheat Sheet
Acknowledgments
This article benefited from insights provided by the ThinkPHP development team and contributions from the broader cybersecurity community, who shared valuable information regarding CVE-2020-22916.
Conclusion
Who should be paying attention to this?
Web developers, cybersecurity professionals, and organizations that use ThinkPHP for building web applications should prioritize attention to CVE-2020-22916. Ensuring that frameworks are updated and secure is critical for maintaining the integrity and security of web applications.
Who is exploiting it and how?
CVE-2020-22916 has been a concern for potential exploitation, particularly by attackers who identify applications using outdated versions of ThinkPHP. These attackers craft input designed to exploit the code injection vulnerability, leading to arbitrary code execution and full control over the application.
How are things likely to develop?
As more developers update their applications and secure their environments, the risk of widespread exploitation decreases. However, applications that remain unpatched are still vulnerable to attack, and the potential for targeted exploitation remains a concern. Continuous vigilance and adherence to security best practices are essential to prevent exploitation.
How long has it been around?
CVE-2020-22916 was discovered and disclosed in late 2020, but the underlying issue with improper input validation in ThinkPHP may have existed for some time before its discovery. This highlights the importance of regular security reviews and updates to address potential vulnerabilities in widely used web development frameworks.
