Understanding And Fixing The Operating System Loader Failed Signature Verification Error on Windows and Linux

In the realm of computers, encountering an error during startup can be a stressful experience. One such error that users across various operating systems like Windows 7, Windows 10, Windows 11, and Linux may face is the “Operating System Loader Failed Signature Verification” error.

This detailed guide will provide an in-depth analysis of what this error means, its common causes, and step-by-step solutions to resolve it efficiently on different operating systems.

Operating System Loader Failed Signature Verification

What Does “Operating System Loader Failed Signature Verification” Mean?

The “Operating System Loader Failed Signature Verification” error typically occurs during the boot process when your computer’s firmware detects that the software, or bootloader, trying to load the operating system has been tampered with or isn’t signed properly.

Digital signatures are used to verify the authenticity and integrity of the software. If the verification fails, it means the digital signature is either missing, corrupted, or not recognized, which leads to the boot process being halted to protect the system’s security.

Common Causes of the Error

The error can be triggered by various factors across different operating systems:

  • Corrupted Bootloader Files: Damage or corruption in the system’s bootloader files can lead to failed signature verification.
  • Outdated or Misconfigured Firmware: Older firmware may not recognize new digital signatures, or misconfigurations can cause it to behave incorrectly.
  • Security Policy Settings: Enhanced security policies or settings that enforce stricter verification models can also trigger these errors, especially if the bootloader has been updated or changed.
  • Malware or Virus Attacks: Malicious software can alter the bootloader, leading to failed verification attempts during the system start.

Step-by-Step Ways to Fix the Error on Windows and Linux

Windows 7/10/11

1. Automatic Repair:

  • Step 1: Restart your PC and insert the Windows installation media.
  • Step 2: Boot from the media and select ‘Repair your computer’.
  • Step 3: Choose ‘Troubleshoot’ and then ‘Automatic Repair’. Follow the prompts to let Windows fix the boot issues.

2. System Restore:

  • Step 1: Access the Advanced Startup options as mentioned above.
  • Step 2: Select ‘System Restore’ and choose a restore point from before the error started occurring.

3. Update or Reset BIOS/UEFI:

  • Step 1: Enter your BIOS/UEFI settings during startup (usually by pressing F2, Del, or Esc).
  • Step 2: Look for an option to update or reset to default settings and follow the specific instructions for your motherboard manufacturer.


1. Repair Bootloader:

  • Step 1: Boot from a live Linux USB or CD.
  • Step 2: Open a terminal and use boot-repair tools like grub-install or update-grub depending on your distribution.

2. Check and Repair Disk Errors:

  • Step 1: Still in the live session, open a terminal.
  • Step 2: Run fsck to check and repair filesystem errors on your Linux partitions.

Fixing Through CMD in Windows

For users comfortable with command line operations, Windows Command Prompt offers a way to potentially resolve the issue:

  • Step 1: Boot using Windows installation media and navigate to ‘Repair your computer’ > ‘Troubleshoot’ > ‘Command Prompt’.
  • Step 2: Type the following commands to repair the Master Boot Record (MBR) and Boot Configuration Data (BCD):
    bootrec /fixmbr
    bootrec /fixboot
    bootrec /rebuildbcd
  • Step 3: Exit and restart the computer.

Using Shortcut Keys

In some cases, accessing BIOS/UEFI settings through shortcut keys during startup allows users to disable strict boot security measures temporarily:

  • Step 1: Repeatedly press F2, Del, or Esc (depending on your system) to enter BIOS/UEFI.
  • Step 2: Locate the ‘Secure Boot’ option and disable it.
  • Step 3: Save and exit the BIOS/UEFI setup.

Additional Considerations and Preventive Measures

Addressing the “Operating System Loader Failed Signature Verification” error is crucial, but it’s equally important to adopt preventive measures to minimize the likelihood of its recurrence.

Here are additional considerations and proactive steps you can take to maintain the integrity of your operating system’s loader.

Regular System Updates

Ensure that your operating system and BIOS/UEFI firmware are regularly updated. These updates often include security patches that can prevent issues related to digital signatures and bootloader integrity.

For Windows, use the Windows Update feature, and for Linux, use your distribution’s package manager to keep the system updated.

Maintain Robust Security Software

Install and maintain robust antivirus and anti-malware software to protect against malicious attacks that could corrupt your bootloader. Regular scans can help detect and remove threats before they cause significant damage to system files.

Backup Critical Data

Regular backups of critical data can save a lot of trouble. In the event of a system failure or error like the “Operating System Loader Failed Signature Verification,” having a recent backup means you can restore your system without losing important data. Use external drives or cloud storage services for backups.

Be Cautious with Third-party Software

Be cautious when installing third-party software, especially those that modify system files or boot configurations. Opt for software from reputable sources and ensure they do not interfere with system boot processes.

Educate Yourself About System Recovery Options

Familiarize yourself with your operating system’s recovery options. Windows users can learn about System Restore, Startup Repair, and the command-line tools available via the Recovery Environment.

Linux users should be comfortable using live CDs or USBs to access repair tools and command-line utilities.

Advanced Troubleshooting Techniques

If the standard repair methods fail, consider these advanced troubleshooting techniques:

Secure Boot and UEFI Firmware Management

For systems using UEFI instead of traditional BIOS, managing Secure Boot settings is crucial:

  • Secure Boot: This feature can prevent unauthorized operating systems from booting. It can be useful for security but might need to be temporarily disabled to troubleshoot signature verification issues.
  • UEFI Settings: Regularly updating your UEFI firmware can resolve incompatibilities with newer operating systems and loaders.

Using Event Viewer in Windows

Windows users can use the Event Viewer to look for specific error messages that occurred at the time of the boot error. This can provide clues about what went wrong and the possible steps to mitigate the issue.

Checking System Logs in Linux

Linux users should check the system logs (/var/log/syslog, /var/log/boot.log) for any anomalies during boot. These logs can provide valuable insights into what might be causing the boot process to fail.


The “Operating System Loader Failed Signature Verification” error is a significant issue that affects the boot process across various operating systems.

By understanding its causes and following the detailed steps outlined for both Windows and Linux, users can effectively troubleshoot and resolve the problem, ensuring a smooth and secure startup of their systems.

FAQ: Operating System Loader Failed Signature Verification Error

Q1: What is an “Operating System Loader Failed Signature Verification” error?

This error occurs when the digital signature of the operating system loader does not pass the verification process during the boot-up sequence. This verification ensures that the loader has not been tampered with and is from a trusted source.

Q2: How does this error affect my computer?

When this error occurs, your computer will fail to boot into the operating system, halting the process to prevent potential security risks. This typically results in seeing an error message on startup and being unable to access your desktop environment.

Q3: What are the common causes of this error on Windows and Linux?

  • Corrupted Bootloader Files: Corruption within the system’s bootloader files.
  • Outdated or Misconfigured Firmware: Firmware that does not recognize or support the current bootloader’s digital signature.
  • Enhanced Security Settings: Settings that may block unrecognized or unsigned bootloaders.
  • Malware Infections: Malicious software that has modified the bootloader.

Q4: Can this error occur on both UEFI and legacy BIOS systems?

Yes, the error can occur on both UEFI (Unified Extensible Firmware Interface) and legacy BIOS systems. However, it is more common on UEFI systems due to the stringent requirements for Secure Boot and signature verification.

Q5: What should I do first if I encounter this error?

The first step should be to attempt a system repair using the built-in repair tools for your operating system. For Windows, you can use Startup Repair, and for Linux, you can repair the GRUB bootloader using a live CD.

Q6: How can I fix this error using Command Prompt in Windows?

You can use the Windows Installation Media to access the Command Prompt and execute commands like bootrec /fixmbr, bootrec /fixboot, and bootrec /rebuildbcd. These commands can help repair bootloader issues.

Q7: Is it safe to disable Secure Boot to fix this error?

Disabling Secure Boot can help in troubleshooting this error as it relaxes the firmware’s security settings allowing potentially unsigned or unrecognized loaders to boot. However, this should be a temporary measure. Once the issue is resolved, re-enable Secure Boot to protect the system against unauthorized changes.

Q8: How can I prevent this error from happening in the future?

Regular system updates, maintaining robust security measures, being cautious with third-party software, and understanding your system’s recovery options are effective strategies to prevent this and similar errors.

Q9: What tools can Linux users utilize to diagnose and fix bootloader issues?

Linux users can use tools like grub-install and update-grub from a live session to repair the GRUB bootloader. Additionally, checking system logs using commands like cat /var/log/syslog can help identify specific issues.

By understanding these FAQs and the detailed guidance provided in the main article, users can effectively manage and resolve the “Operating System Loader Failed Signature Verification” error, ensuring their systems remain secure and functional.