FACEIT "System is missing important Windows security updates" — Full Fix (2026)

On launch, FACEIT Anti-Cheat throws "System is missing important Windows security updates" and refuses to start. It is the single most common FACEIT AC error on Windows 10, and it hits Windows 11 too after a fresh install or a skipped update. The fix is almost always "get Windows fully up to date" — but the error is stubborn: sometimes Windows says it is current while FACEIT disagrees. This guide walks every reliable fix in order, with the exact tools and download links.

What this error actually means

FACEIT AC requires up-to-date Windows security protocols to verify your system. In practice that means a supported Windows build with the latest cumulative security update installed. The minimum today is Windows 11 22H2; FACEIT recommends 23H2 or newer. Windows 10 still works on its last version (22H2) with all updates — but not for long. If your build is older, or the newest security KB is not installed, you get this error.

Step 1 — check your Windows version

Press Win + R, type winver and hit Enter. The dialog shows your edition, version (e.g. 23H2) and OS build. Match it against this table:

Step 2 — the 5-minute fix (works for most)

1. Open Windows UpdateSettings → Windows Update (or press Win and type "Check for updates"). Click Check for updates and install every update offered, security ones first.
2. Install Optional updates tooWindows Update → Advanced options → Optional updates. Install anything listed here — the update FACEIT wants often hides in this list.
3. Restart — twiceReboot, then check for updates again and install whatever appears. Windows delivers updates in waves, so a second pass matters.
4. Relaunch FACEIT ACIf the error is gone, you are done. If it persists, continue below.

Step 3 — if Windows Update is stuck or errors

If Update hangs, errors out, or insists you are "up to date" while FACEIT disagrees, repair the update components first.

1. Repair system filesOpen Command Prompt as administrator and run, in order: DISM /Online /Cleanup-Image /RestoreHealth then sfc /scannow. Let each finish.
2. Reset Windows UpdateStill in admin cmd: net stop wuauserv · net stop bits · clear the cache with ren %windir%\SoftwareDistribution SoftwareDistribution.old · then net start wuauserv · net start bits.
3. Force a scanRun usoclient StartScan (or open Windows Update and Check for updates), then install everything and reboot.

Step 4 — force the latest build with the Installation Assistant

This is the most reliable fix when Update won't cooperate. The Windows 11 Installation Assistant does an in-place upgrade to the newest build without deleting your files or apps.

1. Check compatibilityDownload and run PC Health Check from aka.ms/GetPCHealthCheckApp to confirm your PC meets the Windows 11 requirements.
2. Download the Installation AssistantGo to the official Windows 11 download page → Windows 11 Installation Assistant → Download Now.
3. Run itLaunch the assistant, Accept and Install, and wait. It pulls the latest build and upgrades in place — a Windows 10 PC jumps straight to Windows 11; a Windows 11 PC moves to the newest revision. It restarts a few times.
4. VerifyWhen it finishes, run winver again — you should be on 23H2 / 24H2. Relaunch FACEIT AC.

Step 5 — install the KB manually (Microsoft Update Catalog)

Use this only if Windows Update genuinely cannot deliver the update. It is finicky, but it can push you over the line.

1. Find the latest KB for your buildOpen the Windows 11 release information page (or the Windows Update history for your version) and note the newest cumulative update KB number for your build — the code listed right after the date.
2. Check your architectureSettings → System → About → System type. Almost always x64 (64-bit). You need the package that matches both your Windows version and architecture.
3. Download itGo to the Microsoft Update Catalog, search that KB number, and download the matching package. The file must be a .msu — not a .cab.
4. Install and rebootDouble-click the .msu, let it install, then restart and relaunch FACEIT AC.

Windows 10? Upgrade to Windows 11

On Windows 10, first make sure you are on the last version (22H2, build 19045) with every update installed — that can be enough for now. But FACEIT is phasing Windows 10 out, so plan the move: run the Windows 11 Installation Assistant for an in-place upgrade, or do a clean install from USB (next section). If your PC fails the Windows 11 check (no TPM 2.0 / unsupported CPU), that is a hardware limit — our FACEIT AC errors guide covers the TPM and Secure Boot side.

Pirated or "debloated" Windows — the real blocker

Last resort — clean install of official Windows 11

1. Get the official ISODownload the Windows 11 ISO from the official Microsoft download page. Do not use third-party "optimized" builds.
2. Make a USB with RufusIn Rufus: select your USB, pick the ISO, set Partition scheme = GPT and Target system = UEFI, then Start.
3. Clean installBoot from the USB with CSM disabled in BIOS, install Windows with a format, then run Windows Update fully.
4. Drivers, then FACEIT ACInstall drivers only from your vendor's site (no DriverPack), then install FACEIT AC and run it as administrator.

Once Windows is current, FACEIT AC should start clean. If a different error appears (Secure Boot, TPM 2.0, Memory Integrity, a fatal code), our FACEIT Anti-Cheat error fixes page covers each one step by step.

FAQ