Description

In an UEFI, Lack of verified boot to certain FV may cause arbitrary code execution.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.2",
  "pubDate": "2026-08-12T01:17:08.060Z",
  "pubdate": "2026-08-12T01:17:08.060Z",
  "executiveSummary": "A critical vulnerability has been identified within UEFI implementations stemming from a lack of verified boot mechanisms applied to specific Firmware Volumes (FV).\nThis security deficiency allows an adversary with appropriate capabilities to bypass secure boot integrity validation routines, leading to arbitrary code execution within the pre-boot firmware environment.\nThe affected systems encompass UEFI-based firmware implementations that fail to cryptographically verify or integrity-check designated Firmware Volumes during the platform initialization phase.\nThe risk implications are severe, as arbitrary code execution at the UEFI privilege level grants the attacker complete control over the underlying hardware platform, persistence across operating system reinstalls, and the capability to subvert all subsequent OS-level security controls, including hypervisors, kernel patch protection, and cryptographic volume encryption.\nAttacker capabilities require local access or a pre-existing vector capable of modifying the unverified Firmware Volume within the system's non-volatile storage or memory during the boot lifecycle.\nSuccessful exploitation requires the ability to supply maliciously crafted code to the unverified Firmware Volume, which the UEFI firmware then executes without validation.",
  "technicalDetails": "The root cause of this vulnerability lies in the improper implementation or omission of cryptographic signature verification and integrity checks for specific Firmware Volumes (FV) processed during the UEFI boot sequence.\nIn a secure UEFI architecture, the Platform Initialization (PI) specification dictates that executable binaries, drivers, and applications contained within Firmware Volumes must be authenticated using cryptographic keys anchored in hardware, such as the platform's secure boot keys stored in non-volatile RAM.\nWhen certain Firmware Volumes are exempted from this validation policy or lack the necessary parsing logic to enforce verification, the DXE (Driver Execution Environment) or PEI (Pre-EFI Initialization) phases load and execute payloads from these volumes indiscriminately.\nThe vulnerable component is the UEFI firmware parsing and dispatch mechanism responsible for loading components from the unverified Firmware Volume.\nThe attack flow proceeds as follows: First, an attacker leverages a persistence mechanism, physical access, or a separate vulnerability to overwrite, modify, or inject malicious code into the targeted, unverified Firmware Volume residing in the system's SPI flash or system memory.\nSecond, during a subsequent system reboot or platform reset, the UEFI boot manager initiates the DXE phase and iterates through the configured Firmware Volumes.\nThird, because the specific Firmware Volume lacks verified boot enforcement, the firmware's dispatcher reads the malicious payload and passes execution control to it without performing cryptographic signature validation or hash verification.\nFourth, the malicious payload executes with elevated pre-boot privileges, typically running in System Management Mode (SMM) or Ring 0 equivalent within the UEFI execution context.\nThe post-exploitation impact includes persistent firmware compromise, bypassing of Secure Boot integrity guarantees, capability to read or modify kernel memory prior to OS handoff, interception of hardware communications, and installation of stealthy bootkits that survive operating system reformatting and disk replacement."
}