Security Intelligence
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At a glance:
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Cisco released security updates on October 7, 2026, to address a critical vulnerability in the NX-API management interface used by some Cisco Nexus switches and Unified Computing System fabric interconnects.
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CVE-2026-76471 allows a remote threat actor to execute code with root privileges or cause an affected device to reload. Exploitation of Nexus switches requires the NX-API feature to be enabled and reachable.
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Identify affected devices, review whether NX-API is enabled, restrict access to management interfaces, and upgrade to a fixed software release.
Threat summary
On October 7, Cisco addressed multiple vulnerabilities across its products, with one critical vulnerability affecting Cisco NX-OS, the operating system used by Cisco Nexus data center switches.
CVE-2026-76471, which received a CVSS score of 9.8, is a heap-based buffer overflow caused by insufficient validation of data sent to NX-API. A specially crafted HTTP request can corrupt memory while NX-API processes the request. Successful exploitation can execute arbitrary code with root privileges or crash processes, causing the device to reload and disrupting network services. Exploitation is remote, requires no user interaction, and has low attack complexity.
NX-API is a management interface within NX-OS that allows administrators and automation tools to send commands and configuration requests to a switch over HTTP or HTTPS. The interface provides programmatic access to functions otherwise available through the NX-OS command-line interface.
The vulnerability affects Nexus 3000 Series switches and Nexus 9000 Series switches operating in standalone NX-OS mode when the devices run a vulnerable software release and have NX-API enabled. NX-API is disabled by default on these platforms. Exploitation requires network access to the interface but does not require authentication, making exposure dependent on both configuration and network reachability.
CVE-2026-76471 also affects Cisco Unified Computing System (UCS) 6300 Series Fabric Interconnects through the Cisco UCS Manager XML API. This interface is enabled by default and supports management of the computing, networking, and storage connections controlled by the fabric interconnect. Exploitation on this platform requires valid low-privileged credentials, which reduces the Cisco severity rating from Critical to High for UCS 6300 deployments specifically.
Analysis
CVE-2026-76471 is particularly notable because it affects the management interface of core data center networking infrastructure rather than a standalone application or service. Cisco Nexus 3000 and Nexus 9000 switches are commonly deployed to provide connectivity between servers, storage systems, virtualization platforms, and other critical network components. Because these devices occupy a central position within enterprise and cloud data center environments, a compromise can have consequences beyond the switch itself.
Nexus 3000 and 9000 switches with NX-API enabled and reachable from untrusted networks face the greatest exposure. Internet access increases the opportunity for direct exploitation, but is not required. A threat actor with access to an administrative network, compromised management host, connected automation platform, or another system able to reach NX-API could also target the interface.
Because NX-API provides access to the operating system responsible for forwarding traffic and maintaining switch configuration, root-level code execution could allow a threat actor to alter configurations, create persistent access, disrupt connectivity, or use the switch as a position from which to reach other systems. The extent of further access depends on management-network segmentation, device permissions, monitoring coverage, and the surrounding network architecture.
On UCS 6300 Series Fabric Interconnects, successful exploitation could provide higher-privileged control over a component that manages connectivity between UCS servers and external network and storage infrastructure. Potential consequences depend on the resources connected to the fabric interconnect and the privileges available through the compromised management plane.
Mitigations
Upgrade affected Nexus and UCS devices to a fixed software release identified through the Cisco advisory and Cisco Software Checker. This corrects the input-validation flaw rather than relying on network controls to contain exposure. UCS 6300 deployments running UCS Software 4.2 or earlier require migration to a fixed release, while version 4.3 is fixed in 4.3(6j).
Identify Nexus 3000 and 9000 switches running standalone NX-OS and use show feature | include nxapi to determine whether NX-API is enabled. Disable NX-API where operational workflows do not require it to remove the vulnerable service from the attack path. Limit access to NX-API and UCS management interfaces to approved administrative and automation systems to reduce remote access while updates are deployed.
Apply Cisco’s Live Protect shield where supported as a temporary control, and monitor for unexpected NX-API requests, process crashes, device reloads, configuration changes, and privileged activity.
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