CVE-2018-6460 in Hotspot Shield
Summary
by MITRE
Hotspot Shield runs a webserver with a static IP address 127.0.0.1 and port 895. The web server uses JSONP and hosts sensitive information including configuration. User controlled input is not sufficiently filtered: an unauthenticated attacker can send a POST request to /status.js with the parameter func=$_APPLOG.Rfunc and extract sensitive information about the machine, including whether the user is connected to a VPN, to which VPN he/she is connected, and what is their real IP address.
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Analysis
by VulDB Data Team • 09/29/2025
The vulnerability described in CVE-2018-6460 represents a critical information disclosure flaw within the Hotspot Shield VPN client software that operates a local web server on the victim machine. This web server listens on the loopback interface at 127.0.0.1:895 and employs JSONP (JSON with Padding) for cross-domain data retrieval, creating a dangerous attack surface that allows unauthenticated remote exploitation. The security issue stems from insufficient input validation and sanitization mechanisms within the web server implementation, specifically in the /status.js endpoint that processes POST requests containing the func parameter. This flaw directly violates security principles established in CWE-20, which addresses improper input validation, and CWE-215, which covers information exposure through hidden files and directories. The vulnerability enables attackers to extract sensitive configuration data without requiring authentication, making it particularly dangerous as it operates within the context of the victim's local machine where the VPN client is running.
The technical exploitation of this vulnerability occurs through a carefully crafted POST request to the /status.js endpoint with the parameter func=$_APPLOG.Rfunc, which allows attackers to bypass normal access controls and retrieve detailed information about the user's VPN connection status. The exposed data includes whether the user is currently connected to a VPN service, the specific VPN provider being used, and the user's real IP address, effectively undermining the fundamental purpose of using a VPN for privacy and anonymity. This information disclosure directly maps to ATT&CK technique T1083, which covers discovery of system information, and T1046, which addresses network service scanning, as attackers can systematically gather intelligence about VPN usage patterns and network configurations. The flaw demonstrates a classic case of insecure direct object reference vulnerability, where the application fails to properly validate user input before processing it, allowing arbitrary data extraction through predictable endpoint access patterns.
The operational impact of this vulnerability extends far beyond simple information disclosure, as it fundamentally compromises the privacy and security assurances that users expect from VPN services. Attackers can use the leaked information to build profiles of VPN usage behaviors, identify users who are connected to specific VPN providers, and potentially correlate this data with other intelligence sources to track user activities across different platforms. The exposure of real IP addresses undermines the primary security benefit of VPN usage, making users vulnerable to targeted attacks, location-based tracking, and other forms of surveillance that the VPN was designed to prevent. This vulnerability also enables advanced persistent threat actors to map VPN usage patterns within organizations, potentially identifying high-value targets or conducting reconnaissance for more sophisticated attacks. The impact is particularly severe because the vulnerability exists in client-side software that users typically trust and do not regularly update, creating a persistent security risk that remains exploitable for extended periods.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and sanitization mechanisms within the web server implementation, ensuring that all user-controlled parameters are properly validated before processing. The most effective remediation involves removing or disabling the vulnerable JSONP functionality, implementing authentication requirements for sensitive endpoints, and ensuring that all web server components only accept requests from authorized sources. Organizations should also consider implementing network segmentation and firewall rules to prevent external access to localhost services, while users should be advised to keep their VPN client software updated and to avoid running unnecessary local web services. The vulnerability highlights the importance of proper security testing and code review practices, particularly for applications that expose local services, and demonstrates the need for adherence to security standards such as those outlined in the OWASP Top Ten and NIST cybersecurity frameworks. Additionally, regular security audits should be conducted to identify and remediate similar issues in other network services and applications that may expose sensitive information through insecure data handling practices.