CVE-2025-21215 in Windows
Summary
by MITRE • 01/14/2025
Secure Boot Security Feature Bypass Vulnerability
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Analysis
by VulDB Data Team • 06/16/2026
This vulnerability represents a critical weakness in the secure boot implementation that allows attackers to bypass the integrity verification mechanisms designed to prevent unauthorized code execution during system startup. The flaw typically manifests when the secure boot process fails to properly validate the digital signatures of boot components, enabling malicious actors to load unsigned or tampered firmware modules. Such bypasses can occur through various attack vectors including exploitation of cryptographic weaknesses, improper certificate validation procedures, or insufficient verification of boot chain integrity. The vulnerability directly impacts the foundational security posture of systems by undermining the trust model that secure boot is intended to establish. According to the CWE taxonomy, this represents a weakness in the secure boot implementation that falls under the category of insufficient verification of cryptographic signatures or improper certificate validation. The operational impact extends beyond simple privilege escalation as it fundamentally compromises the system's ability to maintain a trusted execution environment from the moment of power-on. Attackers can leverage this vulnerability to install rootkits, modify bootloaders, or deploy persistent malware that survives operating system reinstallation. The ATT&CK framework categorizes this under initial access and persistence techniques where adversaries establish footholds that are difficult to detect and remove. The vulnerability often stems from implementation flaws in the Unified Extensible Firmware Interface (UEFI) secure boot protocols, where developers may have overlooked edge cases in signature validation or failed to implement proper certificate revocation checking. Organizations running systems with vulnerable secure boot implementations face significant risk of supply chain attacks, where attackers compromise the boot process before any operating system-level protections can be activated. The exploitation typically requires physical access or remote attack capabilities that can manipulate firmware components, making it particularly dangerous in environments where system integrity is paramount. Remediation involves updating firmware to versions that properly implement signature verification, enabling proper certificate chain validation, and implementing additional boot integrity checks that can detect and prevent unauthorized modifications. Security teams must also consider implementing hardware-based security features such as Platform Trust Technology or Trusted Platform Modules that provide additional layers of protection beyond traditional software-based secure boot mechanisms. The vulnerability highlights the importance of comprehensive firmware security testing and validation processes that consider not just the cryptographic implementation but also the operational aspects of secure boot deployment across diverse hardware platforms and firmware versions.