CVE-2022-20795 in ASA
Summary
by MITRE • 04/21/2022
A vulnerability in the implementation of the Datagram TLS (DTLS) protocol in Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause high CPU utilization, resulting in a denial of service (DoS) condition. This vulnerability is due to suboptimal processing that occurs when establishing a DTLS tunnel as part of an AnyConnect SSL VPN connection. An attacker could exploit this vulnerability by sending a steady stream of crafted DTLS traffic to an affected device. A successful exploit could allow the attacker to exhaust resources on the affected VPN headend device. This could cause existing DTLS tunnels to stop passing traffic and prevent new DTLS tunnels from establishing, resulting in a DoS condition. Note: When the attack traffic stops, the device recovers gracefully.
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Analysis
by VulDB Data Team • 07/28/2023
The vulnerability identified as CVE-2022-20795 represents a critical denial of service weakness within Cisco's security infrastructure, specifically affecting Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) platforms. This issue stems from flawed implementation of the Datagram Transport Layer Security protocol, which is fundamental to secure communication channels in network security devices. The vulnerability manifests when these devices process DTLS tunnel establishment as part of AnyConnect SSL VPN connections, creating a pathway for malicious actors to exploit resource consumption patterns that were not adequately addressed in the original protocol implementation. The flaw demonstrates a classic example of inefficient resource management where the system's response to legitimate DTLS traffic processing becomes exponentially resource-intensive under attack conditions.
The technical exploitation of this vulnerability occurs through the manipulation of DTLS packet processing routines that handle the initial handshake and tunnel establishment phases of AnyConnect VPN connections. When an attacker sends sustained crafted DTLS traffic to the affected device, the system's processing logic becomes overwhelmed with computational overhead that scales poorly with the volume of incoming packets. This suboptimal processing behavior creates a resource exhaustion scenario where the device's CPU utilization reaches critical levels, effectively consuming all available processing capacity for legitimate VPN operations. The vulnerability's impact is particularly severe because DTLS is a critical component of the SSL VPN infrastructure, making it impossible for legitimate users to establish new connections while existing connections may be disrupted. This behavior aligns with CWE-400, which addresses resource exhaustion vulnerabilities in software implementations, specifically highlighting the inadequate handling of resource allocation during protocol processing.
The operational consequences of this vulnerability extend beyond simple service disruption to create a comprehensive denial of service condition that affects the entire VPN infrastructure of affected organizations. Network administrators face the challenge of maintaining secure remote access capabilities while the system becomes increasingly vulnerable to sustained attack patterns that can be executed with minimal resources. The recovery mechanism, while graceful, does not provide immediate service restoration, meaning that organizations must either wait for the attack traffic to cease or implement manual intervention procedures to restore normal operations. This vulnerability particularly affects enterprises that rely heavily on remote access capabilities, as the disruption can impact business continuity and employee productivity. The attack vector demonstrates the importance of network segmentation and access control measures, as the vulnerability can be exploited from external networks without requiring authentication credentials, making it particularly dangerous in environments with exposed security appliances.
Mitigation strategies for CVE-2022-20795 should focus on both immediate defensive measures and long-term architectural improvements to prevent resource exhaustion conditions. Organizations should implement rate limiting mechanisms at network boundaries to control the volume of DTLS traffic reaching vulnerable devices, while also applying Cisco's official security patches that address the underlying processing inefficiencies. Network monitoring solutions should be enhanced to detect unusual CPU utilization patterns that may indicate exploitation attempts, providing early warning capabilities for security teams. The implementation of intrusion prevention systems with signature-based detection for known attack patterns can help prevent successful exploitation attempts. Additionally, organizations should consider implementing redundant security infrastructure to ensure that the failure of one device does not completely compromise remote access capabilities for the entire organization. The vulnerability underscores the necessity of regular security assessments and the importance of maintaining updated security software to protect against known exploitation techniques that leverage protocol implementation weaknesses. This case demonstrates the critical importance of proper resource management in network security devices and the potential for seemingly minor implementation flaws to create significant operational impacts.