Fix OSS_DATA_ERROR 0x80093005 in Windows

The 30-Second Fix: Refresh the Certificate or Smart Card

This error pops up when a program — usually Outlook, a VPN client, or a smart card driver — tries to decode an ASN.1 structure and fails. The culprit here is almost always a stale or corrupted certificate in memory.

What to do:

1. Close the app showing the error. I mean fully close it — check the system tray.
2. If you're using a smart card, pull it out, wait 10 seconds, then reinsert it.
3. Reboot your machine. Yes, the standard IT answer. But it clears the certificate cache and reloads drivers. I've seen this fix it instantly after a 30-second restart.

If that doesn't work, move to the moderate fix. Don't bother with driver updates yet — they rarely help here.

The 5-Minute Fix: Reinstall the Certificate

When the quick refresh fails, the problem is a bad certificate in your personal store or the machine store. This happens a lot with certificates that expired, got imported incorrectly, or came from a buggy app.

Step 1: Open the Certificate Manager

certlm.msc

Press Win + R, type that, hit Enter. This opens the machine-level certificate store. If you're a standard user (not admin), use certmgr.msc instead for your user store.

Step 2: Find the bad certificate

Look under Personal > Certificates first. Sort by the Intended Purposes column. Find any certificate with a red X or marked as "not trusted" — that's your target. Also check Trusted Root Certification Authorities > Certificates for expired roots. Error 0x80093005 often comes from a broken client cert, not a root one.

Step 3: Delete and reimport

Right-click the suspect certificate and choose Delete. Then get the original .cer or .pfx file — probably from your IT team or the app's setup folder. Import it fresh:

1. Right-click the Certificates folder (under Personal), choose All Tasks > Import.
2. Follow the wizard. For .pfx files, you'll need the password. Don't check "Mark this key as exportable" unless you need to back it up.

Test the app again. If the error's gone, you're done. If not, proceed to the advanced fix.

The Advanced Fix (15+ Minutes): Repair the Certificate Store

This error can also mean the entire store is corrupted — a rare but real situation I've seen after botched Windows updates or third-party certificate management tools. You'll need to rebuild the store.

Step 1: Run System File Checker

sfc /scannow

Open CMD as admin (Win + X > Terminal Admin). Run that. Let it finish. It'll replace corrupted system files, including store-related DLLs. This takes 5-10 minutes.

Step 2: Reset the certificate store using certutil

certutil -store My
certutil -store Root

These commands list your personal and root stores. If you see any entries marked as EXPIRED or NOT_TRUSTED, note their serial number. Then delete them:

certutil -delstore My "serial_number"
certutil -delstore Root "serial_number"

Step 3: Rebuild the store from scratch (nuke option)

If the store is still broken, backup your certificates first (export them as .pfx with private keys). Then delete the store files manually:

del %APPDATA%\Microsoft\SystemCertificates\My\Certificates\* /q
del %APPDATA%\Microsoft\SystemCertificates\Root\Certificates\* /q

Reboot. Then reimport your backups via certlm.msc. This deletes all personal and root certs — be careful. Only do this if you're comfortable restoring them.

Step 4: Check for application-specific issues

Some apps bundle their own ASN.1 parser that's outdated. For example, older Cisco VPN clients or VMware Horizon will throw 0x80093005 if their certificate libraries are old. Update the app or reinstall it. I've seen this fix it when nothing else worked.

What causes 0x80093005 in real life?

Here's a concrete scenario: A user on Windows 11 Pro 22H2 tries to authenticate to their company VPN using a YubiKey smart card. The card has a valid certificate, but the Windows certificate store has a corrupted copy from an earlier failed enrollment. The ASN.1 decoder chokes on the corrupted data, and you get 0x80093005. The fix: delete the bad cert from the Personal store, reinsert the smart card, let Windows re-read the cert fresh.

Pro tip: If you see this error multiple times on the same machine, suspect a failing smart card reader or a dying certificate on the card itself. Replace the card if deleting and reinserting doesn't work.

When to give up and reinstall Windows

Honestly, I've only needed to do this once in 14 years. If you've tried all three steps above and the error still shows up in a fresh user profile, you're looking at a deep OS corruption. A repair install (keep files) fixes it in under an hour. Skip the full reset — keep your data intact.

That's it. Start with the 30-second fix, move up as needed. This error is stubborn but not a showstopper.