Executive Summary
CVE-2026-76455 is an improper access control weakness (CWE-284) in Cisco NX-OS carrying a CVSS score of 9.8, disclosed through an internal Cisco engineering security review. In OT environments where NX-OS switches often form the backbone between the enterprise boundary and process control zones, an access control bypass at this severity can collapse the segmentation that keeps plant and substation traffic contained.
Technical Exposure Breakdown
The vulnerability is classified under CWE-284, improper access control. At a 9.8 score the defining characteristics are consistent: network-reachable attack vector, low attack complexity, and impact across confidentiality, integrity, and availability without requiring privileges or user interaction. In practical terms, this is the profile of a flaw that lets an unauthenticated actor reach functions or data that should sit behind an authorization boundary.
The GROUNDING DATA does not specify affected NX-OS versions, hardware platforms, or the exact feature path, so we will not guess at those details. What matters for the practitioner is the weakness class and the fact that it was surfaced by Cisco's own hardening review rather than external exploitation. Internally discovered access control defects in NX-OS historically touch management plane services, API endpoints, or role based access control enforcement. Any of those, broken on a core switch, undermine the assumption that only authorized operators can view or alter the device.
Note that CVE-2026-76455 is not currently listed in the known exploited vulnerability catalog. Absence from the KEV program does not lower the engineering priority. A 9.8 access control bypass on a device that sits at a trust boundary is a structural problem regardless of observed exploitation.
OT Impact and Compliance Risk
NX-OS platforms are common in data center and aggregation layers that increasingly carry industrial traffic as utilities and manufacturers consolidate networks. When one of these switches enforces the separation between an IT zone and a control zone, an access control failure has physical consequences. An attacker who reaches management functions can alter VLAN assignments, ACLs, routing, or port configurations. That is the mechanism by which segmentation between a corporate network and a process control network can be dissolved without touching a single PLC directly.
From a standards perspective, IEC 62443 zone and conduit models depend on the integrity of the enforcement devices. If the switch enforcing a conduit can be reconfigured or bypassed, the documented segmentation becomes fiction. For NERC CIP registered entities, an NX-OS device inside an Electronic Security Perimeter falls under CIP-005 and CIP-007 obligations, and an unpatched 9.8 access control flaw on such an asset is a defensible audit finding and a real exposure. Pipeline operators under TSA SD-02C face similar expectations around network segmentation and access control that this flaw directly threatens. Water and wastewater utilities under AWIA 2018 risk assessment obligations should treat core switching as part of the critical asset inventory this vulnerability touches.
Compensating Controls
Do not run an active vulnerability scan against production NX-OS devices sitting in a control path. Aggressive probing of management services can destabilize switch control planes and disrupt the traffic those switches carry to field equipment. Validate exposure through configuration review and passive inspection instead.
- Restrict management plane access. Confine NX-OS management interfaces, API, and administrative services to a dedicated out of band management network unreachable from process and enterprise segments.
- Tighten control plane policing and apply access control lists that limit which source addresses can reach the management plane. An improper access control flaw is far less reachable when the service itself is not exposed.
- Deploy network detection at conduit boundaries. A Suricata concept here watches for unexpected management protocol traffic (NX-API, SSH, SNMP, HTTPS administration) originating from non-management source ranges toward switch management addresses, and alerts on configuration-altering sessions that do not match the known administrator inventory.
- Verify role based access control enforcement and audit for any accounts or sessions with privileges that do not map to a known operator.
These controls reduce reachability while you confirm affected versions against Cisco's advisory and schedule remediation inside an approved maintenance window. Patching a core switch in an OT path is a change control event, not a same-day action, so the virtual patch and access restriction approach buys the time that process continuity requires.
BreachSpider Intel footer: BreachSpider tracks CVE-2026-76455 and related NX-OS access control exposure across industrial network cores so OT teams can monitor affected-version confirmation and exploitation signals as they develop.