CVE-2018-7572 in Pulse Secure
Summary
by MITRE
Pulse Secure Client 9.0R1 and 5.3RX before 5.3R5, when configured to authenticate VPN users during Windows Logon, can allow attackers to bypass Windows authentication and execute commands on the system with the privileges of Pulse Secure Client. The attacker must interrupt the client's network connectivity, and trigger a connection to a crafted proxy server with an invalid SSL certificate that allows certification-manager access, leading to the ability to browse local files and execute local programs.
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Analysis
by VulDB Data Team • 03/23/2020
The vulnerability identified as CVE-2018-7572 represents a critical authentication bypass flaw in Pulse Secure Client software versions 9.0R1 and 5.3RX prior to 5.3R5. This vulnerability specifically affects configurations where the client is set to authenticate VPN users during Windows logon processes, creating a dangerous attack vector that undermines fundamental Windows security mechanisms. The flaw operates through a sophisticated chain of exploitation that leverages network connectivity interruption and proxy server manipulation to gain unauthorized system access.
The technical implementation of this vulnerability stems from improper handling of network connectivity failures within the Pulse Secure Client authentication process. When the client experiences network interruption during authentication, it fails to properly validate the security context of subsequent connection attempts. This failure creates an opportunity for attackers to intercept the authentication flow and redirect it through a malicious proxy server that presents an invalid SSL certificate. The vulnerability specifically exploits the certification-manager access point, which serves as a critical control mechanism for certificate validation and trust establishment within the client software.
The operational impact of CVE-2018-7572 extends beyond simple privilege escalation to encompass complete system compromise. Attackers who successfully exploit this vulnerability can execute arbitrary commands on the target system with the same privileges as the Pulse Secure Client process, which typically operates with elevated permissions due to its role in system authentication. This privilege level allows for extensive system manipulation including local file browsing, program execution, and potential lateral movement within the network. The vulnerability essentially creates a backdoor that bypasses Windows authentication entirely, rendering standard Windows security controls ineffective against this specific attack vector.
This vulnerability aligns with CWE-284, which addresses improper access control, and demonstrates characteristics consistent with attack patterns documented in the MITRE ATT&CK framework under privilege escalation and persistence techniques. The attack requires specific environmental conditions including network interruption and the ability to control or manipulate proxy server configurations, making it more sophisticated than typical credential theft attacks. The exploitation process involves network reconnaissance to identify vulnerable client configurations, followed by precise timing of network disruption and proxy server manipulation to achieve the authentication bypass.
Organizations should implement immediate mitigations including updating to Pulse Secure Client versions 5.3R5 or later, which contain patches addressing the certificate validation flaws. Network administrators should also consider implementing stricter proxy server controls and monitoring for unauthorized proxy configurations. The vulnerability highlights the importance of proper certificate validation mechanisms and demonstrates the risks associated with authentication bypass attacks that exploit client-side software flaws. Security teams should conduct comprehensive vulnerability assessments to identify all instances of affected Pulse Secure Client installations and ensure proper network segmentation to limit potential exploitation impact.