CVE-2020-28502 in xmlhttprequest
Summary
by MITRE • 03/06/2021
This affects the package xmlhttprequest before 1.7.0; all versions of package xmlhttprequest-ssl. Provided requests are sent synchronously (async=False on xhr.open), malicious user input flowing into xhr.send could result in arbitrary code being injected and run.
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Analysis
by VulDB Data Team • 03/28/2021
The vulnerability identified as CVE-2020-28502 affects the xmlhttprequest package version 1.6.0 and earlier, including all versions of the xmlhttprequest-ssl package. This security flaw resides in the handling of synchronous XMLHttpRequest operations where the async parameter is set to false. The vulnerability represents a critical code execution risk that can be exploited through improper input validation in the xhr.send() method. The issue stems from the package's failure to properly sanitize user input when processing synchronous requests, creating an environment where malicious data can be interpreted as executable code rather than plain text data.
The technical implementation of this vulnerability involves the package's XMLHTTPRequest handler not adequately validating or escaping user-supplied data before processing it in synchronous mode. When developers set async=False in xhr.open() calls, the package executes requests synchronously, which creates a window where untrusted input can be injected into the execution context. This flaw aligns with CWE-94, which describes improper control of generation of code, specifically when user input flows directly into code execution contexts without proper sanitization. The vulnerability is particularly dangerous because synchronous XMLHttpRequest operations block the execution thread, making it easier for malicious payloads to maintain control and execute arbitrary commands on the target system.
The operational impact of this vulnerability extends beyond simple code injection, potentially allowing attackers to execute arbitrary commands on systems running vulnerable applications. This type of vulnerability can be exploited in web applications that utilize the xmlhttprequest package for server communication, particularly in environments where user input is processed through XMLHttpRequest calls. The attack vector typically involves an attacker providing malicious input through a form or API endpoint that gets passed to the xhr.send() method. Once executed, the malicious code can perform actions such as data exfiltration, system command execution, or further exploitation of the underlying infrastructure. This vulnerability is categorized under the ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1203 for Exploitation for Client Execution, making it a significant threat in modern application security landscapes.
Mitigation strategies for CVE-2020-28502 require immediate package version updates to 1.7.0 or later, which contain the necessary patches to address the input validation issues. Organizations should conduct comprehensive code reviews to identify all instances where xmlhttprequest is used with synchronous operations, particularly those involving user input. The recommended approach includes implementing proper input sanitization and validation before any data is passed to xhr.send() methods, using parameterized queries, and avoiding synchronous XMLHttpRequest operations where possible. Additionally, developers should consider migrating away from synchronous requests entirely due to their inherent security risks and performance implications. Security monitoring should include detection of unusual XMLHttpRequest patterns and input validation failures to identify potential exploitation attempts. The vulnerability serves as a reminder of the critical importance of input validation in web applications and the necessity of keeping third-party libraries updated to prevent exploitation of known security flaws.