CVE-2020-4041 in Bolt
Summary
by MITRE
In Bolt CMS before version 3.7.1, the filename of uploaded files was vulnerable to stored XSS. It is not possible to inject javascript code in the file name when creating/uploading the file. But, once created/uploaded, it can be renamed to inject the payload in it. Additionally, the measures to prevent renaming the file to disallowed filename extensions could be circumvented. This is fixed in Bolt 3.7.1.
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Analysis
by VulDB Data Team • 10/22/2020
The vulnerability identified as CVE-2020-4041 affects Bolt CMS versions prior to 3.7.1 and represents a stored cross-site scripting flaw that arises from improper input validation during file name handling. This vulnerability specifically targets the file management functionality of the content management system, where user-supplied data can be manipulated to execute malicious scripts in the context of other users who view the affected files. The security issue stems from inadequate sanitization of file names during the renaming process, creating a persistent vector for XSS attacks that can affect multiple users within the CMS environment.
The technical exploitation of this vulnerability occurs through a multi-step process that begins with the initial file upload and continues through the renaming functionality. While direct injection of javascript code into file names during the upload phase is prevented, the flaw allows attackers to manipulate file names after the initial upload by exploiting weak validation controls during the renaming operation. The vulnerability's root cause lies in the insufficient filtering of file extensions and naming conventions, enabling attackers to append malicious payloads to file names that could be executed when the files are accessed or displayed within the CMS interface. This stored XSS vulnerability operates under CWE-79 which specifically addresses cross-site scripting flaws in web applications.
The operational impact of CVE-2020-4041 extends beyond simple script execution, as it can enable attackers to perform session hijacking, steal administrative credentials, or manipulate content within the CMS environment. When users navigate to pages displaying the renamed files, their browsers execute the stored malicious scripts, potentially leading to unauthorized access to sensitive administrative functions or data exfiltration. The vulnerability's persistence stems from the fact that the malicious payloads remain embedded in the file names until explicitly removed, making it particularly dangerous in multi-user environments where administrators and content creators may inadvertently trigger the XSS payloads when viewing or managing files.
Security professionals should note that this vulnerability aligns with ATT&CK technique T1566.001 which covers credential access through social engineering and manipulation of user interfaces. The attack surface expands when considering that administrators may be tricked into clicking on maliciously renamed files, potentially leading to privilege escalation or complete system compromise. The vulnerability also demonstrates weaknesses in the principle of least privilege and input validation within web applications, as the CMS fails to properly sanitize user-supplied data at multiple touchpoints in the file management workflow. Organizations should implement immediate mitigations including upgrading to Bolt CMS version 3.7.1, implementing additional file name validation rules, and conducting security reviews of all file management functionalities within their content management systems to prevent similar vulnerabilities from being introduced in future deployments.