CVE-2023-40985 in Webmin
Summary
by MITRE • 09/15/2023
An issue was discovered in Webmin 2.100. The File Manager functionality allows an attacker to exploit a Cross-Site Scripting (XSS) vulnerability. By providing a malicious payload, an attacker can inject arbitrary code, which is then executed within the context of the victim's browser when any file is searched/replaced.
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Analysis
by VulDB Data Team • 01/30/2026
The vulnerability identified as CVE-2023-40985 represents a critical cross-site scripting flaw within Webmin version 2.100's File Manager component. This issue arises from inadequate input validation and sanitization mechanisms that fail to properly filter malicious payloads submitted through the file search and replace functionality. The vulnerability exists in the web application's user interface where file operations are processed, creating an attack surface that can be exploited by remote malicious actors without requiring authentication or elevated privileges. The flaw specifically manifests when the application processes user-supplied data during file management operations, particularly during search and replace actions where the system fails to properly escape or encode user input before rendering it in the browser context.
The technical exploitation of this vulnerability follows a standard XSS attack pattern where an attacker crafts a malicious payload containing JavaScript code that gets executed within the victim's browser session. The vulnerability is classified under CWE-79 as "Improper Neutralization of Input During Web Page Generation ('Cross-Site Scripting')", which represents one of the most common and dangerous web application security flaws. When a victim performs a search or replace operation within the File Manager, the application renders the malicious input without proper sanitization, allowing the injected script to execute in the victim's browser context with the privileges of the authenticated user. This creates a persistent threat vector that can be leveraged for session hijacking, credential theft, or further exploitation of the compromised system.
The operational impact of CVE-2023-40985 extends beyond simple script execution, as it provides attackers with the ability to manipulate the victim's browser session and potentially access sensitive system information. The vulnerability can be exploited through various attack vectors including phishing emails, compromised websites, or by leveraging other vulnerabilities in the web application ecosystem. Attackers can craft payloads that redirect victims to malicious sites, steal session cookies, or inject additional malicious code that persists across user sessions. The attack chain typically follows the pattern of initial access through a compromised web application interface, followed by session manipulation and potential privilege escalation within the Webmin environment. According to ATT&CK framework, this vulnerability maps to T1059.007 for "Command and Scripting Interpreter: JavaScript' and T1566.001 for 'Phishing: Spearphishing Attachment', demonstrating the multi-faceted nature of the threat landscape.
Mitigation strategies for CVE-2023-40985 should prioritize immediate patching of the Webmin application to version 2.101 or later, which contains the necessary fixes for the XSS vulnerability. System administrators should implement comprehensive input validation and output encoding mechanisms within the application's File Manager component to prevent malicious payloads from being processed. Network-level protections including web application firewalls and content filtering systems can provide additional layers of defense against exploitation attempts. Security monitoring should be enhanced to detect unusual file operations or search patterns that may indicate exploitation attempts. The vulnerability also highlights the importance of regular security assessments and penetration testing to identify similar flaws in web application interfaces. Organizations should enforce principle of least privilege access controls and implement multi-factor authentication to limit the potential impact of successful exploitation attempts, while maintaining detailed audit logs of all file management operations for forensic analysis purposes.