If you have launched 007 First Light and received the message “File Integrity Check Failed: Hash Mismatch for 007firstlight.exe,” the game’s protection system has detected that the main executable does not match its expected cryptographic hash value. This 007 First Light hash mismatch error means the game considers its own executable either corrupted, modified, or tampered with, and it refuses to launch until the integrity of 007firstlight.exe is verified and restored.

This guide covers every verified fix for the 007 First Light file integrity check failed hash mismatch error on Windows PC.

What Causes File Integrity Check Failed Hash Mismatch for 007firstlight.exe

  • Antivirus software modifying or quarantining 007firstlight.exe after scanning it
  • A failed or interrupted game update leaving the executable in a partially written state
  • Disk errors causing bit-level corruption in the executable file
  • Windows Defender real-time protection scanning and altering the executable mid-write during an update
  • Controlled Folder Access interfering with the executable write process during installation
  • Third-party software injecting into or modifying 007firstlight.exe at runtime
  • The executable becoming corrupted after an abrupt system shutdown during a game update
  • Overlays or monitoring software attaching to the executable and altering its hash signature

How to Fix 007 First Light File Integrity Check Failed Hash Mismatch

Fix 1: Add 007firstlight.exe to Antivirus Exclusions Before Verifying

Antivirus software is the primary cause of hash mismatch errors. It modifies or quarantines 007firstlight.exe during scans, altering the file’s hash value. Adding exclusions before verifying prevents the cycle from repeating.

Steps:

  • Open Windows Security and navigate to Virus and Threat Protection Settings
  • Click Add or Remove Exclusions and select Add an Exclusion, then File
  • Navigate to the 007 First Light installation directory and select 007firstlight.exe specifically
  • Also add the entire installation folder as a folder exclusion
  • For third-party antivirus, navigate to the equivalent exclusion section and add the same paths
  • Proceed to Fix 2 after adding exclusions to restore the clean executable

Fix 2: Verify Integrity of Game Files

After adding antivirus exclusions, verifying game files replaces the hash-mismatched 007firstlight.exe with a clean, server-verified version that matches the expected cryptographic hash.

Steps:

  • Open Steam and navigate to your game library
  • Right-click 007 First Light and select Properties
  • Go to the Local Files tab and click Verify Integrity of Game Files
  • Allow Steam to complete the full verification process
  • Steam will detect the hash mismatch in 007firstlight.exe and redownload it automatically
  • Restart Steam and relaunch 007 First Light after verification completes

Fix 3: Restore 007firstlight.exe from Antivirus Quarantine

If 007firstlight.exe was quarantined rather than modified in place, restoring it from quarantine and adding an exclusion prevents the hash mismatch from recurring.

Steps:

  • Open your antivirus software and navigate to the Quarantine or Threats section
  • Search for 007firstlight.exe in the quarantined items list
  • If found, select it and choose Restore or Restore and Allow
  • Immediately add the file and its parent folder to the antivirus exclusions list
  • Restart your PC and relaunch 007 First Light

Fix 4: Disable Controlled Folder Access During Updates

Controlled Folder Access interfering with the executable write process during game updates produces hash mismatches by leaving 007firstlight.exe in a partially written state that does not match the expected hash.

Steps:

  • Press Win + I and go to Privacy and Security, then Windows Security
  • Select Virus and Threat Protection, scroll to Ransomware Protection
  • Click Manage Ransomware Protection and toggle Controlled Folder Access to Off
  • Update or verify 007 First Light while Controlled Folder Access is disabled
  • Re-enable Controlled Folder Access after the update or verification completes

Fix 5: Check and Repair Disk Errors

Disk-level bit corruption on the drive where 007 First Light is installed causes hash mismatches by altering the executable’s content below the file system level.

Steps:

  • Open Command Prompt as Administrator
  • Run the following command replacing C: with your installation drive letter: chkdsk C: /f /r
  • Type Y if prompted to schedule the check on next restart
  • Restart your PC and allow the disk check to complete before Windows loads
  • After Windows boots, verify 007 First Light game files through Steam

Fix 6: Disable All Overlays and Monitoring Software

Third-party overlays and monitoring tools that attach to game processes can alter 007firstlight.exe in memory and on disk, producing a hash mismatch during the integrity check.

Steps:

  • Disable Discord overlay through Discord Settings, then Overlay
  • Turn off Xbox Game Bar through Win + G then Settings
  • Close MSI Afterburner, RivaTuner Statistics Server, and any hardware monitoring tools
  • Disable NVIDIA or AMD overlay features through their respective software panels
  • End all overlay related processes through Task Manager before launching 007 First Light

Fix 7: Perform a Clean Reinstall of 007 First Light

If the hash mismatch persists after all fixes, a complete clean reinstall ensures 007firstlight.exe is written fresh from the server with a verified hash that matches the expected value.

Steps:

  • Uninstall 007 First Light through Steam completely
  • Navigate to the installation directory and delete any remaining folders manually
  • Press Win + R, type %localappdata%, and remove any 007 First Light related folders
  • Restart your PC before reinstalling
  • Reinstall 007 First Light to a drive without disk errors
  • Add antivirus exclusions before launching for the first time

Conclusion

The 007 First Light “File Integrity Check Failed: Hash Mismatch for 007firstlight.exe” error is a corrupted executable detection caused by antivirus interference, disk errors, overlay injection, and interrupted updates. Work through the remaining fixes if the integrity check failure continues. With 007firstlight.exe restored to its verified state and protected from future interference, the file integrity check will pass and the game will launch cleanly.