CVE-2012-5717 in ASA
Summary
by MITRE
Cisco Adaptive Security Appliances (ASA) devices with firmware 8.x through 8.4(1) do not properly manage SSH sessions, which allows remote authenticated users to cause a denial of service (device crash) by establishing multiple sessions, aka Bug ID CSCtc59462.
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Analysis
by VulDB Data Team • 12/21/2021
Cisco Adaptive Security Appliances ASA devices running firmware versions 8.x through 8.4(1) contain a critical vulnerability in their Secure Shell implementation that enables authenticated remote attackers to trigger a denial of service condition. This flaw resides in the SSH session management mechanism where the device fails to properly handle concurrent session connections, creating a resource exhaustion scenario that ultimately leads to device instability and potential system crash. The vulnerability specifically affects the SSH daemon's ability to maintain session state information when multiple connections are established simultaneously, creating a condition where session resources are not properly released or managed. This weakness aligns with CWE-400, which categorizes improper resource management as a fundamental issue in software security. The attack vector requires an authenticated user with valid credentials, making it a privilege escalation scenario that can be exploited by malicious insiders or attackers who have gained initial access to the device. The operational impact extends beyond simple service disruption as the device crash can result in complete network availability loss, particularly in environments where ASA appliances serve as primary security gateways and network access controls. Organizations relying on these devices face significant risk of network outages and potential compromise of security policies when this vulnerability is exploited. The flaw demonstrates a classic resource exhaustion attack pattern that can be categorized under ATT&CK technique T1499.004, specifically targeting availability through resource consumption. The vulnerability affects the core functionality of the ASA's security services, potentially leaving networks exposed to attacks during the device recovery period. The issue represents a failure in proper session lifecycle management within the SSH implementation, where the device does not adequately implement session limiting or resource allocation controls to prevent malicious or accidental overconsumption of system resources. This creates a condition where legitimate users may be unable to establish new SSH connections while the device is recovering from the resource exhaustion state. The impact is particularly severe in enterprise environments where ASA devices are critical infrastructure components, as the device crash can disrupt network access controls, firewall rules, and overall security posture. Organizations should implement immediate mitigation strategies including firmware updates to versions that address the session management flaw, along with monitoring for unusual SSH session patterns that could indicate exploitation attempts. The vulnerability underscores the importance of proper session handling in security appliances and highlights the need for robust resource management practices in network security devices. Security teams must also consider implementing additional controls such as SSH session limiting, connection rate limiting, and monitoring for abnormal session behavior to prevent exploitation of this weakness. This flaw demonstrates how seemingly minor implementation details in security software can result in significant operational impacts, emphasizing the critical nature of proper resource management in security infrastructure components.