Executive Summary

CVE-2023-53950 is a critical vulnerability in InnovaStudio WYSIWYG Editor 5.4 and earlier that allows attackers to bypass file extension restrictions during file uploads by manipulating filenames. Specifically, attackers use null byte injection and alternate file extensions to upload malicious ASP shell files through the asset manager. This unrestricted file upload flaw enables attackers to execute arbitrary code on the server without needing any privileges, user interaction, or authentication. [1, 2]

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Compliance Impact

This vulnerability allows attackers to upload and execute malicious files on the affected system, potentially leading to unauthorized access, data breaches, and compromise of confidentiality, integrity, and availability of data. Such impacts can result in non-compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive data and secure system operations. Therefore, exploitation of this vulnerability could lead to violations of these regulations due to unauthorized data access or system compromise. [1, 2]

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Impact Analysis

This vulnerability can have severe impacts including allowing attackers to upload and execute malicious web shells on the server, leading to remote code execution. Attackers can gain full control over the web server, potentially compromising confidentiality, integrity, and availability of the system. They can also bypass directory privacy by uploading malicious configuration files, escalate privileges, and maintain persistence. Additionally, if other services like SmarterMail are present and misconfigured, attackers can compromise those as well. [1, 2]

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Detection Guidance

This vulnerability can be detected by checking for the presence of uploaded files with suspicious extensions such as .asp, .aspx, or .php in directories intended for asset uploads, especially if filenames contain null byte characters or alternate extensions (e.g., shell.asp%00asp.txt). You can scan the upload directories (e.g., Editor/assets or App_Data) for such files. Commands to detect suspicious files on a Windows server might include: 1) Using PowerShell to find files with double extensions or null byte patterns: Get-ChildItem -Path 'C:\Inetpub\vhosts\pentest.com\httpdocs\Editor\assets' -Recurse | Where-Object { $_.Name -match '\.asp%00' -or $_.Name -match '\.aspx%00' } 2) Checking web server logs for requests to suspicious paths like /editor/assets/shell.asp or /App_Data/shell.aspx. 3) Using curl or wget to test access to known shell paths, e.g., curl https://yourdomain.com/editor/assets/shell.asp. These steps help identify if malicious shells have been uploaded and are accessible. [2]

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Mitigation Strategies

Immediate mitigation steps include: 1) Restrict file upload permissions to prevent unauthorized uploads, ensuring directories like Editor/assets and App_Data have strict write permissions. 2) Implement proper server-side validation to reject files with dangerous extensions and disallow null byte injection in filenames. 3) Configure the web server (IIS) to prevent execution of scripts in upload directories, especially App_Data, by enforcing appropriate web.config settings. 4) Monitor and remove any suspicious uploaded files such as shells or malicious web.config files. 5) Apply any available patches or updates from InnovaStudio for the WYSIWYG Editor. 6) Review and harden permissions on related services like SmarterMail to prevent similar exploitation. These steps reduce the risk of attackers uploading and executing malicious code via this vulnerability. [2]

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