CVE-2015-4239 in ASA
Summary
by MITRE
Cisco Adaptive Security Appliance (ASA) Software 9.3(2.243) and 100.13(0.21) allows remote attackers to cause a denial of service (device reload) by sending crafted OSPFv2 packets on the local network, aka Bug ID CSCus84220.
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Analysis
by VulDB Data Team • 07/03/2017
The vulnerability described in CVE-2015-4239 represents a critical denial of service flaw within Cisco Adaptive Security Appliance software versions 9.3(2.243) and 100.13(0.21). This weakness specifically targets the OSPFv2 routing protocol implementation within the ASA platform, creating a scenario where remote attackers can exploit network communication patterns to force device restarts. The flaw manifests when maliciously crafted OSPFv2 packets are transmitted across the local network segment, triggering an unexpected system behavior that results in complete device reload operations. This vulnerability directly impacts network infrastructure availability and can potentially disrupt critical business operations that depend on continuous network services.
The technical mechanism behind this vulnerability involves improper input validation within the ASA's OSPFv2 packet processing logic. When the appliance receives malformed or specially crafted OSPFv2 packets, the system fails to properly handle the malformed data structures, leading to memory corruption or unexpected state transitions within the routing protocol daemon. This processing failure ultimately triggers an automatic system restart sequence that cannot be prevented through normal operational procedures. The vulnerability operates at the network protocol level, specifically targeting the open shortest path first version 2 implementation that Cisco ASA devices use to communicate routing information with neighboring network devices. According to CWE classification, this represents a weakness in input validation and memory safety, specifically categorized under CWE-129 Input Validation and CWE-787 Out-of-bounds Write.
The operational impact of CVE-2015-4239 extends beyond simple service disruption to encompass potential business continuity risks and network infrastructure stability concerns. Organizations relying on Cisco ASA devices for network security and routing functions face significant operational challenges when this vulnerability is exploited, as device reloads can occur without warning and may affect multiple network segments. The remote nature of the attack means that adversaries need not have physical access to the network infrastructure, making this vulnerability particularly dangerous in environments where network segmentation is not properly implemented. Network administrators may experience extended downtime during recovery periods while system logs are analyzed and device configurations are restored, potentially affecting critical network services and user connectivity. This vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service, specifically targeting network infrastructure availability through device-level disruption.
Mitigation strategies for this vulnerability require immediate implementation of software updates from Cisco, specifically targeting the affected ASA software versions mentioned in the advisory. Organizations should prioritize patching their ASA devices with the latest security releases that address the OSPFv2 packet handling flaws. Network segmentation and access control measures can provide additional protection by limiting the attack surface and preventing unauthorized access to network segments where ASA devices operate. Implementing network monitoring solutions that can detect anomalous OSPFv2 packet patterns may help identify exploitation attempts before they succeed. Additionally, organizations should consider disabling OSPFv2 functionality on ASA devices when it is not strictly required for network operations, reducing the potential attack vectors available to adversaries. The implementation of proper network access controls and firewall rules that limit OSPFv2 packet transmission to trusted network segments can further minimize exposure to this vulnerability. Regular security assessments and network traffic analysis should be conducted to identify and remediate similar weaknesses in network infrastructure components.