CVE-2019-19367 in FusionPBX
Summary
by MITRE
A cross-site scripting (XSS) vulnerability in app/fax/fax_files.php in FusionPBX 4.4.1 allows remote attackers to inject arbitrary web script or HTML via the id parameter.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 03/05/2024
This cross-site scripting vulnerability exists within the FusionPBX 4.4.1 web application, specifically in the fax_files.php script located in the app/fax/ directory. The flaw represents a classic server-side input validation failure where user-supplied data from the id parameter is not properly sanitized before being rendered in the web response. This vulnerability falls under CWE-79 which categorizes improper neutralization of input during web page generation, making it a direct descendant of the fundamental web security principle that all user inputs must be treated as untrusted and validated before processing. The attack vector is particularly concerning as it allows remote exploitation without authentication requirements, enabling malicious actors to inject arbitrary web scripts or HTML content directly into the victim's browser context.
The technical implementation of this vulnerability stems from the application's failure to implement proper input sanitization mechanisms for the id parameter. When a user submits a request containing an id parameter, the system processes this input and incorporates it directly into the dynamic web page generation without adequate filtering or encoding. This creates a persistent XSS condition where the injected script executes in the context of the victim's browser session, potentially allowing attackers to steal session cookies, perform actions on behalf of users, or redirect them to malicious sites. The vulnerability demonstrates poor secure coding practices that violate the principle of least privilege and proper input validation as outlined in the OWASP Top Ten security framework.
The operational impact of this vulnerability extends beyond simple script injection, as it provides attackers with a foothold for more sophisticated attacks within the targeted environment. An attacker could leverage this vulnerability to execute malicious scripts that harvest user credentials, manipulate the application's functionality, or serve as a launching point for further attacks within the network. The attack surface is particularly broad given that FusionPBX is a telephony management platform used in enterprise environments, meaning that successful exploitation could compromise critical communication infrastructure. This vulnerability aligns with ATT&CK technique T1566 which describes social engineering tactics involving the delivery of malicious content, and T1059 which covers command and scripting interpreters, as the injected scripts can execute arbitrary commands within the victim's browser context.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term architectural improvements. The most direct solution involves implementing proper input validation and output encoding for all user-supplied parameters, specifically ensuring that the id parameter in fax_files.php is sanitized before any rendering occurs. This should include implementing Content Security Policy headers to prevent unauthorized script execution, employing proper HTML entity encoding for all dynamic content, and utilizing parameterized queries or input sanitization libraries to prevent injection attacks. Organizations should also consider implementing web application firewalls to detect and block malicious payloads, conduct regular security code reviews focusing on input validation, and establish proper patch management procedures to ensure timely remediation of similar vulnerabilities. The fix should align with the principle of defense in depth, combining multiple security controls to protect against this specific vulnerability while strengthening overall application security posture.