Cisco Unified Computing System UEFI Shell improper authorization

Summaryinfo

A vulnerability was found in Cisco Unified Computing System and Unified Computing System E-Series Software. It has been classified as very critical. The impacted element is an unknown function of the component UEFI Shell. This manipulation causes improper authorization. This vulnerability is handled as CVE-2026-20293. It is possible to launch the attack on the local host. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in Cisco Unified Computing System and Unified Computing System E-Series Software (unknown version) and classified as very critical. Affected by this vulnerability is an unknown code block of the component UEFI Shell. The manipulation with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at sec.cloudapps.cisco.com. This vulnerability is known as CVE-2026-20293 since 10/08/2025. The exploitation appears to be easy. An attack has to be approached locally. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD at the moment (estimation calculated on 09/08/2026). MITRE ATT&CK project uses the attack technique T1548.002 for this issue.

Upgrading eliminates this vulnerability.

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Productinfo

Type

• Virtualization Software

Vendor

• Cisco

Name

• Unified Computing System
• Unified Computing System E-Series Software

License

• commercial

Website

• Vendor: https://www.cisco.com/

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