CVE-2021-23562 in plupload
Summary
by MITRE • 12/03/2021
This affects the package plupload before 2.3.9. A file name containing JavaScript code could be uploaded and run. An attacker would need to trick a user to upload this kind of file.
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Analysis
by VulDB Data Team • 12/09/2021
The vulnerability identified as CVE-2021-23562 affects the plupload package version 2.3.8 and earlier, representing a critical security flaw that enables arbitrary code execution through malicious file uploads. This issue stems from insufficient input validation and sanitization mechanisms within the file upload process, creating a pathway for attackers to bypass security controls and execute malicious JavaScript code on target systems. The vulnerability specifically targets the filename handling component of the plupload library, which is widely used in web applications for file upload functionality.
The technical flaw manifests when the plupload package fails to properly validate or sanitize filenames that contain embedded JavaScript code. This weakness allows an attacker to craft specially formatted filenames that, when processed by the upload mechanism, can execute malicious scripts in the context of the victim's browser session. The vulnerability operates under CWE-434, which categorizes insecure file upload handling as a critical security risk, and aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments. The flaw essentially creates a server-side code execution vector where uploaded files containing malicious JavaScript can be executed without proper authorization, potentially leading to complete system compromise.
The operational impact of this vulnerability extends beyond simple code execution, as it enables attackers to perform various malicious activities including data exfiltration, session hijacking, and privilege escalation. When users upload files containing malicious JavaScript, the code executes in the browser context of the victim, potentially allowing attackers to steal session cookies, redirect users to malicious sites, or inject additional malware. The attack requires social engineering to trick users into uploading the malicious files, but once successful, the attacker gains persistent access to the victim's session and can manipulate the application's behavior. This vulnerability is particularly dangerous in environments where users have elevated privileges or where the application processes uploaded files with elevated permissions.
Mitigation strategies for CVE-2021-23562 involve multiple layers of defense including immediate package updates to version 2.3.9 or later, where the vulnerability has been patched. Organizations should implement robust input validation and sanitization measures that reject or sanitize filenames containing potentially dangerous characters or script tags. Network segmentation and monitoring can help detect suspicious upload activities, while web application firewalls can provide additional protection against malicious file uploads. The fix addresses the root cause by implementing proper filename validation that prevents JavaScript execution during the upload process, aligning with security best practices outlined in OWASP Top Ten and NIST cybersecurity frameworks. Regular security audits and dependency updates remain essential to prevent similar vulnerabilities in other components of the application stack.