CVE-2019-1693 in ASA
Summary
by MITRE
A vulnerability in the WebVPN service of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper management of authenticated sessions in the WebVPN portal. An attacker could exploit this vulnerability by authenticating with valid credentials and accessing a specific URL in the WebVPN portal. A successful exploit could allow the attacker to cause the device to reload, resulting in a temporary DoS condition.
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Analysis
by VulDB Data Team • 09/12/2023
The vulnerability identified as CVE-2019-1693 represents a critical denial of service flaw within Cisco's Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) software platforms. This weakness specifically targets the WebVPN service component, which serves as a critical gateway for remote access to network resources. The vulnerability stems from inadequate session management mechanisms within the WebVPN portal, creating a pathway for authenticated attackers to manipulate the system's operational state. Security professionals must understand that this issue affects organizations relying on Cisco's security infrastructure for remote access control, making it particularly concerning for enterprises with distributed workforces and remote access requirements.
The technical exploitation of CVE-2019-1693 occurs through a carefully crafted sequence involving valid authentication credentials and specific URL access patterns within the WebVPN portal interface. Attackers with legitimate user accounts can leverage this flaw by navigating to particular endpoints that trigger improper session handling within the software's memory management subsystem. This vulnerability operates at the application layer and specifically targets the session lifecycle management functions, where the software fails to properly validate or terminate authenticated connections. The flaw essentially creates a condition where the system's internal session tracking mechanisms become corrupted or overwhelmed, leading to system instability and ultimately requiring a device restart to restore normal operations.
The operational impact of this vulnerability extends beyond simple service disruption, creating significant risks for organizations relying on continuous network access. When exploited successfully, the vulnerability forces affected devices to undergo a complete system reload, resulting in temporary denial of service for all users relying on the WebVPN service. This disruption can cascade through enterprise networks, affecting business continuity, remote worker productivity, and critical system availability. Organizations with mission-critical infrastructure dependent on ASA or FTD appliances face particular risk, as the DoS condition can last from several minutes to hours depending on the device's recovery process. The vulnerability's authentication requirement means that only legitimate users with valid credentials can exploit it, but this still represents a significant insider threat or compromised account risk.
Mitigation strategies for CVE-2019-1693 should prioritize immediate patch application from Cisco, as the vendor released security updates addressing the session management flaw. Network administrators must implement strict access controls and monitoring of WebVPN portal activities to detect anomalous behavior patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-200, which addresses improper error handling and session management issues, and maps to ATT&CK technique T1078 for valid accounts and T1499 for endpoint denial of service. Organizations should also consider implementing additional security controls such as rate limiting on WebVPN access, enhanced logging and monitoring of session management events, and network segmentation to limit the potential impact of successful exploitation. Regular security assessments and vulnerability scanning should be conducted to identify any other related session management weaknesses within the network infrastructure.