CVE-2017-6609 in ASA
Summary
by MITRE
A vulnerability in the IPsec code of Cisco ASA Software could allow an authenticated, remote attacker to cause a reload of the affected system. The vulnerability is due to improper parsing of malformed IPsec packets. An attacker could exploit this vulnerability by sending malformed IPsec packets to the affected system. Note: Only traffic directed to the affected system can be used to exploit this vulnerability. This vulnerability affects systems configured in routed firewall mode only and in single or multiple context mode. This vulnerability can be triggered by IPv4 and IPv6 traffic. An attacker needs to establish a valid IPsec tunnel before exploiting this vulnerability. This vulnerability affects Cisco ASA Software running on the following products: Cisco ASA 1000V Cloud Firewall, Cisco ASA 5500 Series Adaptive Security Appliances, Cisco ASA 5500-X Series Next-Generation Firewalls, Cisco ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers, Cisco Adaptive Security Virtual Appliance (ASAv), Cisco Firepower 9300 ASA Security Module, Cisco ISA 3000 Industrial Security Appliance. Fixed versions: 9.1(7.8) 9.2(4.15) 9.4(4) 9.5(3.2) 9.6(2). Cisco Bug IDs: CSCun16158.
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Analysis
by VulDB Data Team • 08/25/2024
The vulnerability described in CVE-2017-6609 represents a critical flaw in Cisco's Adaptive Security Appliance (ASA) software that affects the Internet Protocol Security (IPsec) implementation. This issue manifests as an improper parsing mechanism within the IPsec code that fails to correctly handle malformed packets, creating a potential denial of service condition that could result in complete system reloads. The vulnerability specifically impacts devices configured in routed firewall mode and operates exclusively when traffic is directed toward the affected system, making it a targeted rather than broadcast vulnerability. The flaw exists across multiple Cisco ASA product lines including the 1000V Cloud Firewall, 5500 Series appliances, 5500-X Next-Generation Firewalls, and various other security modules, indicating a widespread impact across the Cisco security portfolio.
The technical exploitation of this vulnerability requires an authenticated attacker who has established a valid IPsec tunnel to the target system, as the malformed packet processing occurs within the context of existing security associations. The attack vector specifically targets the IPsec packet parsing logic where malformed packets cause the system to crash and subsequently reload, effectively rendering the security appliance unavailable for its intended protective function. This vulnerability demonstrates a classic buffer over-read or improper input validation flaw that can be categorized under CWE-129, which deals with insufficient validation of length of inputs to ensure they are within acceptable bounds. The exploitation process requires the attacker to craft specific malformed IPsec packets that trigger the parsing error, with the vulnerability being equally exploitable through both IPv4 and IPv6 traffic streams, expanding the potential attack surface.
From an operational perspective, this vulnerability poses significant risk to organizations relying on Cisco ASA appliances for network security, as the denial of service condition would compromise the availability of critical security services. The impact extends beyond simple service interruption since the affected systems would require manual intervention to restore functionality, potentially leaving network segments unprotected during the recovery period. The vulnerability affects systems in both single and multiple context modes, meaning that organizations with complex security configurations are equally at risk, and the requirement for a pre-established IPsec tunnel suggests that this vulnerability would be more commonly encountered in environments where IPsec is actively used for secure communications. The attack scenario aligns with ATT&CK technique T1499.004, which involves network disruption attacks through service availability, and represents a significant concern for organizations operating in regulated environments where security appliance availability is critical.
Organizations should prioritize immediate remediation through the application of Cisco's fixed versions, which include releases 9.1(7.8), 9.2(4.15), 9.4(4), and 9.5(3.2), with the specific bug ID CSCun16158 tracking the resolution efforts. The mitigation strategy should involve comprehensive testing of the updated software in non-production environments before deployment to ensure compatibility with existing network configurations. Network administrators should also implement monitoring solutions to detect unusual traffic patterns that might indicate attempted exploitation, particularly around IPsec tunnel establishment and packet processing activities. Additionally, organizations should consider implementing network segmentation to limit the potential impact of such vulnerabilities and ensure that IPsec tunnels are properly secured with strong authentication mechanisms to reduce the likelihood of unauthorized access to the security appliance. The vulnerability serves as a reminder of the critical importance of proper input validation and the potential for seemingly minor parsing flaws to result in significant operational disruptions in security infrastructure components.