CVE-2026-76501 in NX-OS
Summary
by MITRE • 10/07/2026
A vulnerability in the Segment Routing over IPv6 (SRv6) 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 and SRv6 features are 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 identified security flaw resides within the Segment Routing over IPv6 Operation, Administration, and Maintenance feature of Cisco NX-OS Software, specifically affecting the NGOAM component. This vulnerability stems from insufficient input validation mechanisms when processing incoming IP traffic destined for interfaces where both NGOAM and SRv6 functionalities are active. The core technical deficiency involves a failure to properly sanitize or verify specific fields within crafted IPv6 packets before they are processed by the network operating system's control plane logic. Because the flaw occurs at the protocol parsing level, it allows an unauthenticated remote attacker to bypass standard authentication requirements entirely. By constructing and transmitting specially designed malicious packets to any IP interface on the affected device, an adversary can trigger memory corruption or logical errors within the NGOAM process. This lack of rigorous boundary checking is a classic example of improper input validation, which frequently leads to severe consequences in network infrastructure software where performance optimizations sometimes compromise security rigor during packet parsing routines.
The operational impact of exploiting this vulnerability is twofold and potentially catastrophic for network stability and integrity. First, the attacker may achieve arbitrary code execution with root privileges on the compromised device. This level of access grants full control over the operating system, allowing the adversary to install backdoors, exfiltrate sensitive configuration data, modify routing tables, or pivot into other segments of the enterprise network. Second, even if code execution is not successfully achieved, the malformed input can cause critical processes within NX-OS to crash. These process crashes typically result in a device reload, leading to a complete denial of service condition. For mission-critical infrastructure relying on SRv6 for traffic engineering and segmentation, such instability disrupts network connectivity and degrades overall service availability. The combination of remote code execution and denial of service makes this vulnerability particularly dangerous as it offers attackers multiple avenues to compromise the confidentiality, integrity, and availability of the targeted system.
From a classification perspective, this issue aligns with CWE-20 Improper Input Validation, which describes failures in checking or filtering input before processing. The attack vector is categorized under ATT&CK technique T1190 Exploit Public-Facing Application, as it leverages vulnerabilities in internet-facing services to gain initial access. Furthermore, the ability to execute arbitrary code with elevated privileges maps directly to CWE-269 Improper Privilege Management and CWE-78 OS Command Injection if shell commands are executed via the root context. The remote nature of the exploit means that no prior authentication or network proximity is required beyond basic IP connectivity, significantly expanding the attack surface compared to local-only vulnerabilities.
Mitigation strategies must prioritize immediate patching through official Cisco software updates that address this specific NGOAM parsing flaw. Until patches are applied, administrators should consider disabling SRv6 and NGOAM features on interfaces where they are not strictly necessary for business operations, thereby reducing the exposure surface. Additionally implementing strict ingress filtering rules to block malformed IPv6 packets or restricting access to management planes via Access Control Lists can provide a layer of defense-in-depth. Network monitoring systems should be configured to detect anomalous traffic patterns indicative of crafted packet attacks targeting SRv6 headers. Regular vulnerability assessments and adherence to CIS benchmarks for network device hardening are essential to maintain resilience against such exploits in modern IPv6-enabled environments.