Fix 0xC0150018: Duplicate Attribute in Side-by-Side Assembly

Quick answer (for advanced users)

Run sfc /scannow then DISM /Online /Cleanup-Image /RestoreHealth in an admin command prompt. If that fails, reinstall the Visual C++ Redistributable packages for your OS version. The root cause is a corrupt manifest file that lists the same attribute twice — Windows can't load the assembly because of that conflict.

What's actually happening here

Error code 0xC0150018 pops up when a Windows side-by-side (SxS) assembly has two definitions for the same attribute. Think of an assembly as a small package containing DLLs and a manifest file — the manifest tells Windows how to load those DLLs. If the manifest says "this DLL needs version 12.0.40660.0" but also says "same DLL needs version 12.0.40661.0" in the same section, Windows doesn't know which one to use. It throws this error.

I've seen this most often with apps that install old Visual C++ runtimes. A game installer from 2015 might drop a manifest that conflicts with a newer runtime already on your system. Or a Windows update partially overwrites a manifest, leaving it half-baked. Either way, the solution is to clean up the corrupted assembly data.

Step-by-step fix

Step 1: Run System File Checker

Open an admin Command Prompt (right-click Start > Command Prompt (Admin) or Terminal (Admin)). Type:

sfc /scannow

Let it finish — takes 10-15 minutes on a modern PC. It checks core system files against the official cached copies. If it finds a damaged manifest or DLL, it replaces it. Reboot after this step.

Step 2: Run DISM to repair the component store

If SFC didn't find anything, the corruption might be in the component store itself. In the same admin prompt, run:

DISM /Online /Cleanup-Image /RestoreHealth

This command downloads fresh copies of system files from Windows Update. It's more thorough than SFC. Takes 20-30 minutes depending on your internet speed. Reboot again.

Step 3: Reinstall all Visual C++ Redistributables

If steps 1+2 didn't fix it, the duplicate attribute is likely in a Visual C++ runtime manifest. Microsoft release these as installable packages. Go to the official Microsoft site for "Latest supported Visual C++ downloads". Download and install both the x64 and x86 versions for 2015-2022 (they're combined now). Also grab 2013 and 2010 if your app is old. Install each one, reboot once after all of them.

The reason this works: reinstalling the runtime replaces the corrupt manifest with a clean copy from the installer. It overwrites any duplicate attributes that got left behind.

Step 4: Repair or reinstall the app

Still broken? The problem is in the app's own manifest, not a system one. Go to Control Panel > Programs & Features, find the app that gives the error, and choose Repair. If no repair option, uninstall it, reboot, and install fresh from the official download.

Alternative fixes if the main ones fail

Clean boot: Disable all non-Microsoft services via msconfig. This isolates conflicts. If the error goes away, a third-party service or driver is corrupting the assembly.
System Restore: Roll back to a point before the error started. Works wonders if you have a restore point from last week.
In-place upgrade: Use the Windows 11/10 "Update now" tool to reinstall Windows while keeping your files and apps. Fixes deep SxS corruption. Takes 1-2 hours but avoids a full wipe.

How to prevent this from coming back

This error mostly comes from bad installers or botched updates. Stick to official app downloads. Don't let apps install their own old runtimes — keep the latest Visual C++ redistributables from Microsoft's site. Run SFC and DISM once a month if you're paranoid. If you use third-party antivirus, make sure it's compatible with your Windows build — I've seen Avast and McAfee corrupt assemblies during real-time scans.

One more thing: the exact error 0xC0150018 appears across all Windows versions from 7 to 11. The fix doesn't change. The only difference is that on Windows 7 you might need to manually download the DISM update if SFC fails.