Bypass Vulnerability in Cisco UCS Servers UEFI Shell Implementation

CVE-2026-20293

What is CVE-2026-20293?

This vulnerability exists in the Unified Extensible Firmware Interface (UEFI) Shell of Cisco UCS Servers and UCS-based appliances. It allows authenticated users, or any individual with physical access to the device, to bypass UEFI Secure Boot validation checks. This occurs due to the presence of memory write commands available in the UEFI Shell. An attacker could exploit this by choosing the UEFI Shell boot option during startup, using shell commands to alter UEFI memory variables. The implications of this exploit include the ability to manipulate the preboot environment, overwrite crucial UEFI Secure Boot memory values, and run unauthorized software on the affected systems.

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