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How CVE-2026-48573 works
CVE-2026-48573 is a protection mechanism failure in Windows Secure Boot that allows a local, authorized attacker to bypass this critical security feature. The root cause lies in a reliance on a non-updateable component (CWE-1329)—namely, the Secure Boot certificates issued back in 2011 that are now expiring. These original certificates are embedded in the UEFI firmware of countless devices and cannot be patched or removed through standard operating system updates. As the certificates approach their expiration dates, the boot‑time trust verification logic that depends on them becomes brittle. An attacker with sufficient privileges can exploit this flaw by using an expiring but still trusted certificate to sign malicious boot components. Secure Boot, which ordinarily verifies digital signatures against a database of trusted certificates, may continue to accept these signed components even after the official validity period has ended, depending on how the system handles the expiration state. Because the expired certificate resides in a non‑updateable region of the firmware, Microsoft cannot directly revoke it; instead, the fix requires a coordinated replacement of the entire certificate chain, which must be delivered through both OS updates and OEM‑specific firmware patches. The failure occurs when an authorized local user (i.e., an attacker who already has a valid account or physical access) manipulates the boot process to load unsigned or maliciously signed drivers, bootloaders, or even a full bootkit before Windows starts. Because Secure Boot is supposed to guarantee that only trusted code executes during the early boot phases, bypassing it breaks the entire platform integrity chain. An attacker can thus gain persistent, low‑level control that outlives operating system reinstalls and remains invisible to most security products. The vulnerability is assigned CVSS 3.1 vector AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N, resulting in a base score of 7.9 (High).
DailyCVE Form:
Platform: Microsoft Windows
Version: Win10/11/Server
Vulnerability : Secure Boot Bypass
Severity: High (7.9)
date: 06/09/2026
Prediction: June 9, 2026
What Undercode Say:
Check Secure Boot status
Confirm-SecureBootUEFI
Enumerate boot configuration
bcdedit /enum all
List installed updates to verify patch
Get-HotFix | Where-Object {$_.HotFixID -like "KB"}
Query UEFI variables (requires admin)
Get-WmiObject -Namespace root\wmi -Class WmiMonitorID
Find expiring Secure Boot certificates (needs OEM tools)
Get-SecureBootUEFI -Name "db"
Exploit:
- Gain local administrator privileges on a vulnerable system.
- Identify a still‑trusted but expiring 2011 Secure Boot certificate in UEFI’s `db` database.
- Use that certificate to sign a custom bootloader or rootkit.
- Replace the legitimate bootloader with the malicious one.
- Reboot; Secure Boot accepts the malicious code as valid.
- Malicious bootloader loads before Windows, disabling further protections.
- Establish persistent, low‑level control with ability to bypass OS‑level security.
Protection:
- Install the June 2026 Windows Update (released June 9, 2026).
- Apply any accompanying OEM firmware update that renews Secure Boot certificates.
- Verify Secure Boot is enabled in UEFI/BIOS (
Confirm-SecureBootUEFI). - Restrict local administrative access and enforce driver signature policies.
- Monitor Event Logs for attempts to alter Secure Boot keys or load unsigned drivers.
Impact:
- Load unsigned bootkits, rootkits, and malicious bootloaders.
- Persist across OS reinstalls and hard drive replacements.
- Steal BitLocker keys, credentials, and encryption keys.
- Disable OS‑level security features like Defender and HVCI.
- Provide hidden communication channel for further payloads.
- Potentially lead to a BlackLotus‑style compromise on fully patched Windows systems.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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