CVE-2026-20033

High

Published: 25 February 2026

Published

25 February 2026

Modified

15 April 2026

KEV Added

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Patch

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CVSS Score v3.1 7.4 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS Score 0.0002 6.0th percentile

Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-20033 is a high-severity Buffer Access with Incorrect Length Value (CWE-805) vulnerability in Cisco Nexus (inferred from references). Its CVSS base score is 7.4 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 6.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SC-7 (Boundary Protection).

Deeper analysis

CVE-2026-20033 is a vulnerability affecting Cisco Nexus 9000 Series Fabric Switches operating in ACI mode. The issue arises from insufficient validation when processing specific Ethernet frames on the out-of-band (OOB) management interface, which could allow an unauthenticated adjacent attacker to trigger a denial of service (DoS) condition. Published on 2026-02-25, it carries a CVSS v3.1 base score of 7.4 (AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H) and maps to CWE-805.

An adjacent attacker can exploit this vulnerability by sending a crafted Ethernet frame to the OOB management interface of an affected device. Successful exploitation causes the device to reload unexpectedly, leading to a DoS condition. Only the OOB management interface is impacted.

The Cisco Security Advisory provides details on mitigation and patches: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-cpdos-qLsv6pFD.

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-8665

Vulnerability details

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.

CWE(s): CWE-805

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1499.004 Application or System Exploitation Impact

Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.

attack.mitre.org →

Why these techniques?

Vulnerability enables unauthenticated adjacent attackers to send crafted frames triggering device reload/crash, directly mapping to endpoint DoS via system exploitation.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1