CVE-2019-9591 in Connect ONSITE
Summary
by MITRE
A reflected Cross-site scripting (XSS) vulnerability in ShoreTel Connect ONSITE before 19.49.1500.0 allows remote attackers to inject arbitrary web script or HTML via the brandUrl parameter.
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Analysis
by VulDB Data Team • 09/14/2025
The vulnerability identified as CVE-2019-9591 represents a critical reflected cross-site scripting flaw within ShoreTel Connect ONSITE software versions prior to 19.49.1500.0. This vulnerability exists in the web application interface where user-supplied input is improperly validated and sanitized before being reflected back to the victim's browser. The specific parameter affected is brandUrl which is processed in a manner that fails to adequately escape or encode user-provided content, creating an avenue for malicious actors to inject arbitrary web scripts or HTML code into the application's response. The reflected nature of this vulnerability means that the malicious payload is immediately reflected from the web server to the victim's browser without being stored on the server, making it particularly dangerous for targeted attacks. This vulnerability falls under CWE-79 which specifically addresses Cross-site Scripting flaws in web applications where input is not properly validated or escaped. The attack vector requires minimal user interaction as the malicious payload is typically delivered through phishing emails or compromised links that when clicked by a victim, execute the injected script in the victim's browser context.
The operational impact of this vulnerability extends beyond simple script injection as it provides attackers with the capability to perform session hijacking, steal cookies, redirect users to malicious sites, or even perform actions on behalf of authenticated users within the application. The ShoreTel Connect ONSITE platform serves as a unified communications solution that handles sensitive business data and user credentials, making this vulnerability particularly dangerous in enterprise environments. Attackers could leverage this flaw to establish persistent access to the system, escalate privileges, or conduct further reconnaissance activities within the network. The vulnerability's presence in the brandUrl parameter suggests that it may be accessible through various configuration or branding interfaces that administrators use to customize the application's appearance and functionality, potentially providing attackers with multiple entry points for exploitation. This aligns with ATT&CK technique T1059.007 which covers scriptlets and command-line interfaces, and T1566 which encompasses social engineering tactics. The vulnerability's exploitation typically requires the victim to interact with a maliciously crafted URL that contains the XSS payload, making it susceptible to phishing campaigns and targeted attacks.
Organizations affected by this vulnerability should immediately implement comprehensive mitigations including input validation, output encoding, and proper sanitization of all user-supplied parameters. The most effective immediate solution involves patching the software to version 19.49.1500.0 or later where the vulnerability has been addressed through proper input validation and sanitization mechanisms. Additionally, implementing Content Security Policy headers can provide an additional layer of defense against XSS attacks by restricting the sources from which scripts can be loaded. Web Application Firewalls should be configured to detect and block suspicious patterns in URL parameters, particularly those containing common XSS attack vectors. Network segmentation and access controls should be reviewed to limit potential lateral movement if an attacker successfully exploits this vulnerability. The implementation of proper logging and monitoring mechanisms can help detect exploitation attempts and provide forensic evidence for incident response activities. Organizations should also conduct security awareness training for administrators and end-users to recognize potential phishing attempts that may leverage this vulnerability, as the attack often relies on social engineering elements to deliver the malicious payload to unsuspecting users.