CVE-2018-5264 in UniFi 52
Summary
by MITRE
Ubiquiti UniFi 52 devices, when Hotspot mode is used, allow remote attackers to bypass intended restrictions on "free time" Wi-Fi usage by sending a /guest/s/default/ request to obtain a cookie, and then using this cookie in a /guest/s/default/login request with the byfree parameter.
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Analysis
by VulDB Data Team • 09/28/2023
The vulnerability CVE-2018-5264 affects Ubiquiti UniFi 52 devices operating in Hotspot mode, representing a critical authentication bypass flaw that undermines the intended access control mechanisms for wireless networks. This issue stems from improper session management and authorization validation within the device's web interface, specifically targeting the guest wireless access functionality that is commonly deployed in enterprise and public Wi-Fi environments. The vulnerability allows remote attackers to circumvent time-based restrictions that are typically enforced to limit free Wi-Fi usage periods, thereby enabling unlimited access to network resources that should be constrained by predefined time limits.
The technical exploitation of this vulnerability involves a two-step process that demonstrates a fundamental flaw in the device's session handling and parameter validation mechanisms. Attackers begin by sending a GET request to the /guest/s/default/ endpoint to obtain a valid session cookie, which serves as the initial credential for the authentication process. This cookie acquisition step reveals a weakness in the device's access control implementation where session tokens are generated without proper validation of user permissions or access rights. Subsequently, the attacker leverages this cookie in a POST request to the /guest/s/default/login endpoint with the byfree parameter, effectively bypassing the time restriction controls that should govern guest network access. This technique exploits a classic session management vulnerability where the system fails to properly validate session tokens against the intended access policies, allowing unauthorized privilege escalation through simple parameter manipulation.
The operational impact of CVE-2018-5264 extends beyond simple unauthorized access, creating significant security implications for organizations relying on UniFi devices for wireless network management. Network administrators who implement time-based restrictions to control bandwidth usage, prevent abuse, and manage network resources effectively find their security controls rendered ineffective, potentially leading to resource exhaustion and service degradation. The vulnerability particularly affects organizations that depend on guest Wi-Fi access for customers, visitors, or employees who should be subject to time limitations, as it enables unlimited access that can result in unauthorized network consumption and potential bandwidth theft. This flaw directly violates security principles of least privilege and proper access control enforcement, as outlined in the CWE-285 category for improper authorization and CWE-305 for authentication bypass techniques.
Organizations utilizing Ubiquiti UniFi devices in Hotspot mode should immediately implement mitigations to address this vulnerability, including applying the latest firmware updates from Ubiquiti that contain patches for the session management flaw. Network segmentation and access control measures should be enhanced to limit the impact of potential exploitation, while monitoring systems should be configured to detect unusual authentication patterns or unauthorized access attempts. The vulnerability aligns with ATT&CK technique T1078 for valid accounts and T1046 for network service scanning, as attackers may use this flaw to establish persistent access or conduct reconnaissance activities within the network. Additionally, organizations should consider implementing web application firewalls and access control lists to prevent unauthorized requests to the vulnerable endpoints, while conducting regular security assessments to identify similar session management vulnerabilities in other network infrastructure components. The remediation process should also include comprehensive network access control reviews and user permission audits to ensure that time-based restrictions are properly enforced across all wireless access points and network devices.