External risk intelligence

Cisco NX-OS Improper Access Control Vulnerabilities.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-76455

The vulnerability affects Cisco NX-OS, a network operating system used in switches and routers. While these devices often sit at the network edge or act as core infrastructure, management interfaces and control plane functions are typically secured behind internal network controls or management VLANs rather than being directly exposed to the public internet by design.

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory concerns multiple, internally discovered vulnerabilities within Cisco NX-OS software. These issues relate to improper access control, meaning unauthorized users could potentially gain elevated privileges or access restricted information. While the full impact depends on specific network configurations and exposure, vulnerabilities of this type can pose significant risks to network integrity and data confidentiality.

Access control flaws found in network software.
Protects core network infrastructure devices.
Confirm relevance and exposure to Cisco NX-OS.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by reaching a vulnerable network management interface or control plane function. This could allow them to gain unauthorized access and potentially manipulate the network device's behavior.

No authentication required.
Network-based access to management interfaces.
Complete compromise of device confidentiality, integrity, and availability.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability, related to improper access control, could allow an unauthenticated, remote attacker to affect the integrity and availability of affected systems, and potentially access sensitive information. These issues are addressed in a software hardening release for Cisco NX-OS.

System integrity and availability.
Network access when supported by advisory.
Potential unauthorized information access.

Operational Fix

Recommended remediation, mitigation, and detection steps

Technical leaders and system owners responsible for Cisco NX-OS deployments must coordinate to address these critical access control vulnerabilities. The first step is to identify all instances of the affected software, confirm their network exposure and business criticality, and then determine the accountable team for remediation. Planning should prioritize systems with the highest exposure and impact, involving vendor coordination and potential maintenance window scheduling.

Network and infrastructure teams own this issue.
Verify system exposure and business criticality.
Plan remediation based on identified risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is Cisco NX-OS software?

Cisco NX-OS is a network operating system designed for data center-class environments. It serves as the core intelligence for high-performance switches and routers, managing data traffic and device operations to ensure reliable connectivity within enterprise networks.

What does CWE-284 mean for CVE-2026-76455?

CWE-284 refers to Improper Access Control. This means the software fails to properly restrict who can access or manipulate certain features. In the context of CVE-2026-76455, it suggests that unauthorized individuals might bypass security checks to interact with device functions that should be off-limits.

How does an attacker trigger this vulnerability?

An attacker triggers this by reaching a vulnerable management interface or control plane function over the network. Crucially, the vulnerability does not require any authentication, meaning a valid user account is not a precondition for a remote attacker to attempt access.

Is my device at risk based on Halo Surface Signal?

Halo Surface Signal indicates that risk is highest if management interfaces are reachable from untrusted networks. While many NX-OS devices are core infrastructure typically protected by management VLANs or internal controls, any device with a management interface exposed to the internet requires immediate attention.

What is the first step to address this CVE?

Begin by inventorying all systems running Cisco NX-OS to understand your footprint. Once identified, evaluate the network placement of these devices, specifically checking if management interfaces are accessible beyond your internal security perimeter, and coordinate with your infrastructure team to plan a software update.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-s…

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.