Cisco Security Advisories

THREAT INTELLIGENCE

Peer Review

4.8

Proven Trust

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High

Cisco

September 9, 2026

Executive Summary

A UEFI Shell vulnerability allows attackers to bypass Secure Boot protections and execute unauthorized software.

Key Details

Affected Platform

Cisco

Attack Surface

Recommended Action

Apply vendor patch

Affected Environment

Cisco UCS Servers, UCS-based appliances, and UCS C-Series based appliances with UEFI Secure Boot enabled.

Operational Impact

Successful exploitation allows execution of unauthorized software and compromises preboot environment integrity.

Technical Root Cause

Availability of memory write commands in the UEFI Shell while Secure Boot is enabled on the device.

Recommended Mitigation

Apply Cisco's fixed firmware releases across all affected UCS servers and appliances as scheduled.

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Full Technical Report

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References

Cisco Security Advisory cisco-sa-ucs-uefi-sb-bypass-eb6xC5GW.