CVE-2018-6320 in Pulse Connect Secure
Summary
by MITRE
A vulnerability has been discovered in login.cgi in Pulse Secure Pulse Connect Secure (PCS) 8.1RX before 8.1R12 and 8.3RX before 8.3R2 and Pulse Policy Secure (PPS) 5.2RX before 5.2R9 and 5.4RX before 5.4R2 wherein an http(s) Host header received from the browser is trusted without validation.
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Analysis
by VulDB Data Team • 03/21/2020
The vulnerability identified as CVE-2018-6320 affects Pulse Secure Pulse Connect Secure and Pulse Policy Secure appliances, representing a critical authentication bypass flaw that exploits improper input validation mechanisms. This vulnerability exists within the login.cgi component of affected versions, where the system fails to properly validate the HTTP Host header received from client browsers, creating a pathway for malicious actors to manipulate authentication flows. The flaw stems from the trust model that assumes all incoming Host headers are legitimate without proper verification, allowing attackers to exploit this trust relationship for unauthorized access to secure networks.
The technical implementation of this vulnerability resides in the HTTP Host header validation process within the authentication subsystem. When a client makes a request to the Pulse Secure appliance, the system receives an HTTP Host header that should contain the fully qualified domain name of the server. However, the vulnerable code trusts this header without performing cryptographic validation or cross-checking against known legitimate endpoints. This trust model creates a condition where an attacker can craft malicious requests with spoofed Host headers that point to internal systems or bypass authentication checks entirely. The vulnerability manifests as a lack of proper input sanitization and validation, which aligns with CWE-20, representing improper input validation in software systems.
The operational impact of this vulnerability extends beyond simple authentication bypass, as it enables attackers to perform session hijacking, conduct man-in-the-middle attacks, and potentially gain access to sensitive network resources. Attackers can exploit this flaw by manipulating the Host header to redirect authentication requests or by using the vulnerability to establish unauthorized sessions with elevated privileges. The affected versions include multiple release streams of Pulse Connect Secure and Pulse Policy Secure appliances, making this vulnerability widespread across different deployment scenarios and network architectures. This vulnerability directly impacts the integrity of the authentication process and compromises the security boundary that these appliances are designed to maintain.
Organizations affected by CVE-2018-6320 should implement immediate mitigations including applying the vendor-provided patches that address the Host header validation issue, implementing network-level controls to monitor and filter suspicious Host header values, and conducting thorough security assessments of their Pulse Secure deployments. The mitigation strategy should include disabling unnecessary HTTP headers, implementing proper input validation mechanisms, and establishing monitoring procedures to detect anomalous Host header patterns. This vulnerability also highlights the importance of following the principle of least privilege and implementing defense-in-depth strategies that do not rely solely on single points of authentication validation. Organizations should consider implementing additional authentication layers and network segmentation to reduce the attack surface and limit potential lateral movement if the vulnerability is exploited. The ATT&CK framework categorizes this type of vulnerability under credential access and initial access techniques, emphasizing the need for robust authentication validation mechanisms and proper header handling within web applications and network security appliances.