CVE-2026-76485 in NX-OS
Summary
by MITRE • 10/07/2026
A vulnerability in the VXLAN Operation, Administration, and Maintenance (OAM) feature of Cisco NX-OS Software, known as NGOAM, could allow an unauthenticated, remote attacker to execute arbitrary code with root privileges or cause a Denial-of-Service (DoS) on an affected device.
This vulnerability is due to improper input validation of IP traffic when the NGOAM feature is enabled. An attacker could exploit this vulnerability by sending crafted packets to an IP interface on an affected device. A successful exploit could allow the attacker to execute arbitrary code with root privileges and could cause process crashes resulting in a reload and DoS condition.
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Analysis
by VulDB Data Team • 10/07/2026
The Cisco NX-OS Software contains a critical security flaw within its VXLAN Operation, Administration, and Maintenance feature, commonly referred to as NGOAM. This vulnerability stems from insufficient input validation when processing IP traffic destined for the management plane or specific network interfaces where the NGOAM functionality is active. The core technical deficiency lies in the failure of the software to properly sanitize or verify the structure and content of incoming VXLAN packets before they are processed by the underlying system routines. Because this feature handles operational data essential for maintaining virtual extensible LAN environments, it requires privileged access to function correctly. However, the lack of rigorous boundary checks on packet headers and payload contents allows an unauthenticated remote attacker to craft maliciously formatted packets that trigger memory corruption or logic errors within the NX-OS kernel space.
From a technical perspective, this flaw represents a classic case of improper input validation leading to arbitrary code execution. When an attacker sends specially crafted VXLAN OAM packets to an affected IP interface, the software attempts to parse these inputs without adequate checks for length, type, or structural integrity. This oversight can result in buffer overflows or heap corruption within the privileged process handling NGOAM traffic. Consequently, a successful exploitation allows the remote adversary to inject and execute arbitrary commands with root-level privileges on the compromised device. Root access provides complete control over the operating system, enabling the attacker to install backdoors, modify configurations, exfiltrate sensitive data, or pivot further into the network infrastructure.
The operational impact of this vulnerability is severe due to its potential for both full system compromise and service disruption. Beyond the risk of arbitrary code execution, the flaw can also be leveraged to cause a Denial-of-Service condition. By sending specific malformed packets that trigger process crashes within critical NX-OS components, an attacker can force the device to reload unexpectedly. This results in significant network downtime, disrupting connectivity for all users and services relying on the affected switch or router. In data center environments where VXLAN is commonly deployed for overlay networking, such instability can lead to widespread outages affecting multiple tenants and applications simultaneously.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-20 Improper Input Validation, as the root cause is the failure to verify that user-supplied data conforms to expected formats before processing. In terms of attack tactics, it maps to MITRE ATT&CK techniques related to Initial Access and Privilege Escalation, specifically leveraging network service vulnerabilities to gain initial foothold and then escalating privileges through memory corruption exploits. The unauthenticated nature of the exploit makes it particularly dangerous as no prior credentials are required for initiation.
To mitigate this risk, organizations running Cisco NX-OS should immediately apply the latest software patches provided by Cisco that address the NGOAM input validation flaw. It is crucial to verify that all devices in the VXLAN overlay network are updated to a non-vulnerable release version. Additionally, while patching is the primary defense, implementing strict access control lists (ACLs) on management interfaces can help limit exposure if immediate patching is not feasible. Restricting UDP port 4789 and related OAM traffic sources to only trusted administrative subnets reduces the attack surface significantly. Regular monitoring of network logs for anomalous VXLAN packet patterns should also be employed to detect potential exploitation attempts in real-time.