CVE-2019-16970 in FusionPBX
Summary
by MITRE
In FusionPBX up to 4.5.7, the file app\sip_status\sip_status.php uses an unsanitized "savemsg" variable coming from the URL, which is reflected in HTML, leading to XSS.
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Analysis
by VulDB Data Team • 01/17/2024
The vulnerability CVE-2019-16970 represents a critical cross-site scripting flaw discovered in FusionPBX versions 4.5.7 and earlier. This issue resides within the sip_status.php application file, specifically in how it handles user input from the URL parameter named "savemsg". The flaw demonstrates poor input validation and output sanitization practices that create an exploitable condition for malicious actors to inject arbitrary HTML code into the application's response. FusionPBX is a web-based interface for managing FreeSWITCH telephony systems, making it a critical component in enterprise communication infrastructures where security is paramount.
The technical implementation of this vulnerability stems from the application's failure to properly sanitize user-supplied data before incorporating it into HTML output. When a user requests a page with a "savemsg" parameter in the URL, the application directly reflects this input without adequate filtering or encoding mechanisms. This creates a classic reflected cross-site scripting scenario where malicious payloads can be executed in the context of a victim's browser session. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws, and aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments or links. The lack of proper input validation means that any data entered through the URL parameter can be interpreted as executable HTML, allowing attackers to inject scripts that can steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users.
The operational impact of this vulnerability extends beyond simple script execution, as it can lead to complete compromise of the FusionPBX administrative interface. An attacker who successfully exploits this vulnerability can gain unauthorized access to the telephony system, potentially enabling them to modify call routing, access voicemail systems, manipulate user accounts, or even redirect calls to malicious numbers. This poses significant risks to enterprise communication networks where FusionPBX serves as the central management interface for voice services. The vulnerability is particularly dangerous because it requires minimal user interaction to exploit, often just clicking a malicious link delivered through phishing emails or social engineering campaigns. Organizations using vulnerable versions of FusionPBX face potential data breaches, service disruption, and compliance violations due to the exposure of sensitive telephony infrastructure.
Mitigation strategies for CVE-2019-16970 must focus on immediate remediation and long-term security hardening of the FusionPBX installation. The primary solution involves upgrading to FusionPBX version 4.5.8 or later, where the input sanitization issue has been addressed through proper parameter validation and HTML encoding. System administrators should also implement input validation at multiple layers, ensuring that all user-supplied data is properly escaped before being rendered in HTML contexts. Network-level protections such as web application firewalls can provide additional defense-in-depth measures by detecting and blocking malicious URL parameters. Security monitoring should be enhanced to detect unusual patterns in URL parameters that might indicate exploitation attempts. The vulnerability highlights the importance of following secure coding practices and implementing proper input/output sanitization as outlined in OWASP Top 10 and NIST cybersecurity guidelines, particularly focusing on the prevention of XSS attacks through proper data validation and output encoding mechanisms.