CVE-2011-1937 in Webmin
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Webmin 1.540 and earlier allows local users to inject arbitrary web script or HTML via a chfn command that changes the real (aka Full Name) field, related to useradmin/index.cgi and useradmin/user-lib.pl.
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Analysis
by VulDB Data Team • 11/08/2021
The vulnerability identified as CVE-2011-1937 represents a critical cross-site scripting flaw within Webmin version 1.540 and earlier installations. This security weakness specifically targets the user management functionality of the web-based system administration tool, creating a pathway for malicious actors to execute arbitrary web scripts or HTML code within the context of other users' browsers. The vulnerability manifests through the chfn command implementation which handles the modification of user real names or full names within the system's user database.
The technical exploitation of this vulnerability occurs through the useradmin/index.cgi and useradmin/user-lib.pl components of Webmin's architecture. When local users manipulate the real name field through the chfn command, the input validation mechanisms fail to properly sanitize the data before it is rendered back to users in the web interface. This failure creates an XSS vector where malicious input can be stored and subsequently executed when other users view the affected user records. The vulnerability is particularly concerning because it leverages legitimate administrative functions to deliver malicious payloads, making detection more challenging and exploitation more likely to succeed.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform session hijacking, steal sensitive information, manipulate user interfaces, or redirect victims to malicious websites. The attack surface is broadened by the fact that Webmin is commonly used for system administration tasks, meaning that any user with local access could potentially exploit this vulnerability. The persistence of the malicious code within the user database means that the XSS payload remains active until the affected records are modified or deleted, providing attackers with extended opportunities for malicious activity.
Security professionals should recognize this vulnerability as a classic example of insufficient input validation and output encoding issues, which aligns with CWE-79 - Improper Neutralization of Input During Web Page Generation. The attack pattern follows typical XSS exploitation methodologies documented in the MITRE ATT&CK framework under technique T1566 - Phishing, where the initial compromise occurs through web-based interfaces rather than traditional phishing vectors. Organizations running affected Webmin versions should prioritize immediate patching and implement proper input sanitization measures to prevent similar vulnerabilities in their own applications. The remediation process requires careful attention to the user management components and comprehensive testing to ensure that all input fields are properly validated and escaped before being rendered in web contexts.