CVE-2019-12693 in ASA
Summary
by MITRE
A vulnerability in the Secure Copy (SCP) feature of Cisco Adaptive Security Appliance (ASA) Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to the use of an incorrect data type for a length variable. An attacker could exploit this vulnerability by initiating the transfer of a large file to an affected device via SCP. To exploit this vulnerability, the attacker would need to have valid privilege level 15 credentials on the affected device. A successful exploit could allow the attacker to cause the length variable to roll over, which could cause the affected device to crash.
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Analysis
by VulDB Data Team • 12/29/2023
The vulnerability identified as CVE-2019-12693 affects the Secure Copy (SCP) functionality within Cisco Adaptive Security Appliance (ASA) Software versions 9.1 through 9.8.1. This issue represents a critical flaw in the software's handling of file transfer operations that could be leveraged by authenticated attackers to disrupt service availability. The vulnerability stems from improper data type management within the SCP implementation, specifically involving a length variable that is susceptible to overflow conditions. According to CWE-190, this corresponds to an integer overflow or wraparound condition where the system fails to properly validate or handle large numeric values, creating a pathway for system instability. The affected devices operate under the assumption that file transfer lengths will remain within reasonable bounds, but the absence of proper boundary checking allows malicious input to trigger unexpected behavior.
The technical exploitation of this vulnerability requires an attacker to possess administrative privileges at privilege level 15, indicating that the flaw does not provide a path for unauthorized access but rather enables an authenticated malicious actor to cause system disruption. When a large file transfer is initiated via SCP to an affected ASA device, the improper handling of the length variable causes it to exceed its maximum representable value and subsequently wrap around to zero or a negative value. This integer overflow condition directly impacts the device's memory management and buffer allocation processes, leading to a system crash that manifests as a denial of service condition. The operational impact extends beyond simple service interruption as the device becomes unavailable for its primary security functions, potentially leaving network traffic unmonitored and unprotected during the recovery period. The vulnerability operates at the application layer of the network stack, specifically within the file transfer protocol implementation, making it particularly concerning for network security infrastructure.
The implications of this vulnerability extend significantly within enterprise network security environments where ASA devices serve as primary security controls. Organizations relying on ASA appliances for network protection face potential operational disruptions when this vulnerability is exploited, as the device crash could occur during critical security operations or maintenance windows. The DoS condition affects the appliance's ability to perform its core security functions including firewalling, intrusion prevention, and network access control, creating potential security gaps during the recovery process. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving denial of service and privilege escalation, though the initial access requirement of privilege level 15 limits its broader impact. The vulnerability demonstrates poor software engineering practices in input validation and integer handling, representing a fundamental security flaw that could be exploited to compromise the availability of critical network infrastructure. Organizations should implement immediate mitigation strategies including access control hardening, monitoring for suspicious SCP activity, and applying the relevant Cisco security patches to address the integer overflow condition in the SCP implementation.