Cisco UCS and UCS-Based Appliances UEFI Shell Secure Boot Bypass Vulnerability

Description

A vulnerability in the Unified Extensible Firmware Interface (UEFI) Shell implementation of Cisco UCS Servers and UCS-based appliances could allow an authenticated attacker with valid credentials for a user account with the role of user or admin or an unauthenticated attacker with physical access to an affected device to bypass UEFI Secure Boot validation checks and execute unauthorized software. This vulnerability is due to the availability of memory write commands in the UEFI Shell while UEFI Secure Boot is enabled on a device. An attacker could exploit this vulnerability by selecting the UEFI Shell boot option at boot time and using available shell commands to modify UEFI memory variables. A successful exploit could allow the attacker to manipulate the preboot environment, overwrite UEFI Secure Boot-related memory values, and execute unauthorized software on the affected device. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ucs-uefi-sb-bypass-eb6xC5GW Security Impact Rating: High CVE: CVE-2026-20293

What to do

Install the fixed versions listed in the official advisory. If you cannot update right away, apply the workarounds or mitigations it describes and limit access to the affected service.

Details

Vendor

Cisco

Product

Cisco UCS

CVE

CVE-2026-20293

Affected versions

Cisco Enterprise NFV Infrastructure Software 4.1: 4.1.1; 4.1.2
Cisco Enterprise NFV Infrastructure Software 3.9: 3.9.1; 3.9.2
Cisco Enterprise NFV Infrastructure Software 3.5: 3.5.1; 3.5.2
Cisco Enterprise NFV Infrastructure Software 3.12: 5 versions, from 3.12.1b to 3.12.3
Cisco Enterprise NFV Infrastructure Software 3.6: 3.6.1; 3.6.2; 3.6.3
Cisco Enterprise NFV Infrastructure Software 3.11: 3.11.1; 3.11.2; 3.11.3
Cisco Enterprise NFV Infrastructure Software 3.3: 3.3.1
Cisco Enterprise NFV Infrastructure Software 3.10: 3.10.1; 3.10.2; 3.10.3
Cisco Enterprise NFV Infrastructure Software 3.4: 3.4.1
Cisco Enterprise NFV Infrastructure Software 3.8: 3.8.1
Cisco Enterprise NFV Infrastructure Software 3.7: 3.7.1
Cisco Enterprise NFV Infrastructure Software 4.2: 4.2.1; 4.2.2
Cisco Enterprise NFV Infrastructure Software 4.4: 4.4.1; 4.4.2; 4.4.3
Cisco Enterprise NFV Infrastructure Software 4.5: 4.5.1
Cisco Enterprise NFV Infrastructure Software 4.6: 6 versions, from 4.6.1 to 4.6.4
Cisco Enterprise NFV Infrastructure Software 4.7: 4.7.1
Cisco Enterprise NFV Infrastructure Software 4.8: 4.8.1; 4.8.2
Cisco Enterprise NFV Infrastructure Software 4.9: 8 versions, from 4.9.1 to 4.9.10
Cisco Enterprise NFV Infrastructure Software 4.10: 4.10.1
Cisco Enterprise NFV Infrastructure Software 4.11: 4.11.1
Cisco Enterprise NFV Infrastructure Software 4.12: 8 versions, from 4.12.1 to 4.12.8
Cisco Enterprise NFV Infrastructure Software 4.13: 4.13.1
Cisco Enterprise NFV Infrastructure Software 4.14: 4.14.1
Cisco Enterprise NFV Infrastructure Software 4.15: 6 versions, from 4.15.1 to 4.15.6
Cisco Unified Computing System (Managed) 4.0: 22 versions, from 4.0(1a) to 4.0(4o)
Cisco Unified Computing System (Managed) 4.1: 22 versions, from 4.1(1a) to 4.1(3n)
Cisco Unified Computing System (Managed) 4.2: 26 versions, from 4.2(1c) to 4.2(3r)
Cisco Unified Computing System (Managed) 4.3: 23 versions, from 4.3(2b) to 4.3(6g)
Cisco Unified Computing System (Managed) 6.0: 8 versions, from 6.0(1b) to 6.0(2c)
Cisco Unified Computing System (Standalone) 4.0: 36 versions, from 4.0(2g) to 4.0(1.260004) (from the advisory and NVD; check the exact builds in the official advisory)

CVSS score

7.1

Actively exploited

Not known at this time

Source

Cisco PSIRT – original advisory

Published

October 13, 2026

The description and the recommended action are quoted from the public advisory (the action is our generic advice); severity, exploitation status and affected versions are compiled automatically from public sources and may contain errors. The vendor's original advisory prevails: check it before taking action. This information is provided without warranty and does not replace a professional assessment.