CVE-2009-4918 in ASA 5580
Summary
by MITRE
Cisco Adaptive Security Appliances (ASA) 5580 series devices with software before 8.1(2) allow remote attackers to cause a denial of service (IKE process hang) via malformed NAT-T packets, aka Bug ID CSCsr74439.
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Analysis
by VulDB Data Team • 04/20/2017
The vulnerability described in CVE-2009-4918 affects Cisco Adaptive Security Appliances (ASA) 5580 series devices operating with software versions prior to 8.1(2). This issue represents a significant denial of service weakness that can be exploited remotely by malicious actors to disrupt network security operations. The vulnerability specifically targets the Internet Key Exchange (IKE) process within the ASA firewall implementation, causing it to hang and effectively rendering the device unable to process legitimate security traffic. The flaw manifests when the device receives malformed Network Address Translation - Tunneling (NAT-T) packets, which are commonly used in IPsec VPN configurations to traverse NAT boundaries. This type of vulnerability directly impacts the availability and reliability of critical network security infrastructure.
The technical implementation of this vulnerability stems from insufficient input validation within the IKE processing module of the ASA software. When malformed NAT-T packets are received, the IKE daemon fails to properly handle the malformed data structures, leading to a process hang condition that prevents further IKE processing. This behavior aligns with CWE-129, which addresses issues related to insufficient validation of input data, and CWE-399, which covers resource management errors. The vulnerability can be exploited from remote locations without requiring authentication, making it particularly dangerous for network security devices that are typically exposed to external traffic. The NAT-T protocol is widely used in enterprise VPN deployments, meaning that exploitation could impact organizations relying on ASA devices for secure remote access and site-to-site connections.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise broader network security posture. When the IKE process hangs, the ASA device cannot establish or maintain IPsec VPN connections, which affects remote worker access, branch office connectivity, and secure communication channels between network segments. This vulnerability creates a window of opportunity for attackers to perform further exploitation attempts or to conduct broader network reconnaissance activities while the device remains unresponsive. Organizations using affected ASA 5580 series devices face potential business disruption, increased administrative overhead for manual device recovery, and possible compliance violations if security controls are compromised. The vulnerability also demonstrates poor defensive programming practices in network security devices, where error handling mechanisms fail to account for malformed packet structures that could be encountered in real-world network traffic.
The mitigation strategy for CVE-2009-4918 involves immediate deployment of Cisco's recommended software updates to version 8.1(2) or later, which contain patches addressing the IKE process hang issue. Network administrators should also implement monitoring solutions to detect unusual IKE traffic patterns that might indicate exploitation attempts. Additional defensive measures include configuring access control lists to limit exposure of ASA devices to potentially malicious NAT-T traffic and implementing network segmentation to reduce the attack surface. From an ATT&CK framework perspective, this vulnerability maps to technique T1499.004, which covers network denial of service attacks, and T1566.002, related to spearphishing via social media. Organizations should also consider implementing intrusion detection systems that can identify malformed NAT-T packets and alert security teams to potential exploitation attempts. The vulnerability underscores the importance of maintaining current security software versions and implementing robust network monitoring practices to detect and respond to similar issues in security infrastructure.