CVE-2018-0231 in ASA
Summary
by MITRE
A vulnerability in the Transport Layer Security (TLS) library of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a reload of the affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient validation of user-supplied input. An attacker could exploit this vulnerability by sending a malicious TLS message to an interface enabled for Secure Layer Socket (SSL) services on an affected device. Messages using SSL Version 3 (SSLv3) or SSL Version 2 (SSLv2) cannot be be used to exploit this vulnerability. An exploit could allow the attacker to cause a buffer underflow, triggering a crash on an affected device. This vulnerability affects Cisco ASA Software and Cisco FTD Software that is running on the following Cisco products: Adaptive Security Virtual Appliance (ASAv), Firepower Threat Defense Virtual (FTDv), Firepower 2100 Series Security Appliance. Cisco Bug IDs: CSCve18902, CSCve34335, CSCve38446.
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Analysis
by VulDB Data Team • 03/03/2023
The vulnerability described in CVE-2018-0231 represents a critical denial of service weakness within Cisco's security infrastructure software ecosystem. This flaw exists in the Transport Layer Security implementation of Cisco Adaptive Security Appliance (ASA) and Cisco Firepower Threat Defense (FTD) platforms, specifically affecting devices running ASA Software and FTD Software across various hardware and virtualized platforms including ASAv, FTDv, and Firepower 2100 Series appliances. The vulnerability stems from inadequate input validation mechanisms within the TLS library that processes secure communication protocols, creating an exploitable condition that can be leveraged by remote attackers without requiring authentication credentials.
The technical exploitation of this vulnerability occurs through the manipulation of SSL/TLS protocol messages sent to interfaces configured for SSL services on affected devices. Attackers can craft malicious TLS messages that trigger a buffer underflow condition within the vulnerable software components, specifically targeting the SSLv3 and SSLv2 protocol implementations. The flaw manifests when the system processes malformed input data that exceeds allocated buffer boundaries, causing memory corruption and subsequent system instability. This particular vulnerability is specifically designed to affect SSL versions 3 and 2, with the more modern TLS protocols remaining unaffected, indicating that the issue is rooted in legacy protocol handling rather than fundamental cryptographic implementation flaws.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromising the availability of critical network security infrastructure. When exploited successfully, the vulnerability forces affected devices to reload their operating systems, effectively creating a denial of service condition that can persist until manual intervention occurs. This disruption can severely impact network security posture, particularly in environments where these devices serve as primary security gateways, firewalls, or threat detection systems. The vulnerability affects organizations that rely on Cisco's security appliances for network protection, potentially leaving critical infrastructure exposed to attack during the service interruption period.
Cisco has identified this vulnerability through internal bug tracking systems under IDs CSCve18902, CSCve34335, and CSCve38446, indicating the severity and scope of the issue. The vulnerability aligns with CWE-121, which describes buffer overflow conditions in heap-based memory management, and represents a classic example of insufficient input validation that can lead to system instability. From an attack framework perspective, this vulnerability maps to MITRE ATT&CK techniques related to service disruption and availability compromise, specifically targeting the availability aspect of the CIA triad. Organizations should consider implementing network segmentation to limit exposure, applying the relevant Cisco security patches, and monitoring for anomalous traffic patterns that might indicate exploitation attempts. The fix typically involves updating to patched versions of ASA and FTD software that include proper input validation mechanisms and buffer management procedures to prevent the underflow conditions that trigger device reloads.