CVE-2026-20033 Cisco NX-OS Software Denial of Service Vulnerability
An unauthenticated adjacent attacker can cause a denial of service on Cisco Nexus 9000 switches in ACI mode by sending crafted Ethernet frames to the management interface.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-20033?
CVE-2026-20033 is a high-severity denial of service vulnerability in Cisco NX-OS System Software in ACI Mode, published on 25 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A vulnerability in Cisco Nexus 9000 Series Fabric Switches in ACI mode could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient validation when processing specific Ethernet frames. An attacker could exploit this vulnerability by sending a crafted Ethernet frame to the management interface of an affected device. A successful exploit could allow the attacker to cause the device to reload unexpectedly, resulting in a DoS condition. Note: Only the out-of-band (OOB) management interface is affected.
Weakness: CWE-805
Which versions are affected by CVE-2026-20033?
How do I fix CVE-2026-20033?
No fix has been published for CVE-2026-20033 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-20033 being exploited?
There is no known exploitation of CVE-2026-20033 in the wild and no public exploit code.
Sources
Also known as GHSA-w865-j4h6-vqm4.