CVE-2020-3528 in ASA
Summary
by MITRE • 10/22/2020
A vulnerability in the OSPF Version 2 (OSPFv2) implementation of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to incomplete input validation when the affected software processes certain OSPFv2 packets with Link-Local Signaling (LLS) data. An attacker could exploit this vulnerability by sending a malformed OSPFv2 packet to an affected device. A successful exploit could allow the attacker to cause an affected device to reload, resulting in a DoS condition.
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Analysis
by VulDB Data Team • 08/12/2026
The vulnerability identified as CVE-2020-3528 represents a critical denial of service weakness within the OSPF Version 2 implementation of Cisco Adaptive Security Appliance and Cisco Firepower Threat Defense software platforms. This flaw resides in the processing of OSPFv2 packets containing Link-Local Signaling data, where the software fails to properly validate incoming packet parameters. The vulnerability affects network security devices that operate as routers or firewalls, making it particularly concerning for enterprise and critical infrastructure environments where continuous network availability is paramount.
The technical root cause of this vulnerability stems from inadequate input validation mechanisms within the OSPFv2 processing module of affected Cisco products. When the software receives OSPFv2 packets with specific Link-Local Signaling data structures, it does not sufficiently validate the packet contents before attempting to process them. This incomplete validation allows malformed packets to traverse the normal processing flow and trigger unexpected behavior in the device's routing engine. The flaw specifically manifests when the software encounters certain combinations of OSPF packet headers and LLS data fields that exceed expected parameter boundaries or contain invalid data structures.
From an operational perspective, this vulnerability creates a significant risk for network availability and business continuity. An unauthenticated remote attacker can exploit this weakness by simply sending a specially crafted OSPFv2 packet to the target device, requiring no prior authentication credentials or network access privileges. The successful exploitation results in an immediate device reload or restart, effectively disrupting network services and potentially causing cascading failures in larger network topologies. The impact extends beyond individual device outages as network routing protocols may experience instability during the reload process, potentially leading to broader network disruption.
The vulnerability aligns with CWE-20, which describes "Improper Input Validation" as a fundamental weakness in software design that allows malformed inputs to bypass validation checks. Additionally, this weakness maps to ATT&CK technique T1499.004, which covers "Domain Generation Algorithm" and related network disruption techniques. The exploitability of this vulnerability is particularly concerning given that OSPF is a widely deployed routing protocol that operates at the network layer, making affected devices vulnerable to attacks from any network segment that can reach the device's OSPF listening interfaces. Organizations using Cisco ASA and FTD products in their network infrastructure should prioritize this vulnerability for remediation as it represents a straightforward path to service disruption without requiring advanced attack capabilities or insider knowledge.
Mitigation strategies for CVE-2020-3528 should include immediate deployment of Cisco's official security patches and advisories, which address the input validation gaps in the OSPFv2 implementation. Network administrators should also consider implementing OSPF packet filtering rules at network boundaries to prevent malformed packets from reaching vulnerable devices, particularly those operating in untrusted network segments. Additional defensive measures include monitoring network traffic for unusual OSPF packet patterns and implementing network segmentation to limit the potential impact of successful exploitation attempts. Regular network security assessments should be conducted to identify any other potential vulnerabilities in routing protocol implementations and ensure comprehensive protection against similar threats.