CVE-2020-7700 in phpjs
Summary
by MITRE
All versions of phpjs are vulnerable to Prototype Pollution via parse_str.
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Analysis
by VulDB Data Team • 11/10/2020
The vulnerability identified as CVE-2020-7700 affects all versions of phpjs, a javascript library that provides php functions for javascript environments. This issue stems from a prototype pollution vulnerability within the parse_str function implementation, which allows attackers to manipulate the prototype of objects through malicious input. The vulnerability exists because the library does not properly validate or sanitize input parameters before incorporating them into object prototypes, creating a pathway for attackers to inject malicious properties into the Object prototype.
Prototype pollution occurs when an attacker can manipulate the prototype of an object in a way that affects all instances of that object throughout the application. In the context of phpjs, the parse_str function processes string data and converts it into objects, but fails to properly handle cases where input data contains keys that could modify the prototype chain. This flaw falls under CWE-471, which specifically addresses the vulnerability of functions that do not properly check for prototype pollution when processing user input. The issue is particularly dangerous because it can affect the entire application runtime environment, as any object that inherits from the polluted prototype will be affected by the malicious modifications.
The operational impact of this vulnerability is significant, as it can lead to various security consequences including but not limited to remote code execution, denial of service attacks, and privilege escalation. When an attacker successfully exploits this vulnerability, they can inject properties into the Object prototype that may be leveraged to manipulate application behavior or execute unintended code. The vulnerability can be exploited through any input that flows through the parse_str function, making it particularly dangerous in web applications that process user-supplied data. This type of attack aligns with ATT&CK technique T1059.007, which involves the use of scripting languages for execution, and T1211, which covers the exploitation of vulnerabilities in software libraries.
Mitigation strategies for CVE-2020-7700 involve immediate updates to the phpjs library to versions that address the prototype pollution vulnerability. Organizations should also implement input validation and sanitization measures to prevent malicious data from reaching the vulnerable functions. Additional protective measures include using secure coding practices such as avoiding direct assignment to prototype properties, implementing proper object cloning techniques, and employing runtime monitoring to detect unusual prototype modifications. Security teams should also conduct thorough code reviews to identify other potential instances of prototype pollution in their applications and dependencies. The vulnerability highlights the importance of proper input validation and the need for security-conscious development practices when working with javascript libraries that provide php function implementations.