Error 0x800F081F means Windows could not find the source files needed to complete a servicing operation.
Microsoft identifies the error as CBS_E_SOURCE_MISSING and describes it as:
the source for a package or file was not found. [R1]
This often appears when Windows is repairing its component store, installing an optional Windows feature, or processing an update that needs files that are not currently available on the PC.
The important distinction is:
0x800F081F does not mean that Windows simply needs another retry. It means the servicing operation could not obtain required source files.
What is a repair source?
A repair source is a trusted location containing known-good Windows component files.
Microsoft documents several possible repair sources, including:
- Windows Update;
- a mounted Windows image;
- a Windows installation shared on a network; or
- a Windows image (
.wim) configured as an alternate repair source. [R2] [R3]
For a normal online Windows installation, Windows Update can be used as the repair source when policy allows it. [R2]
If the required files are not available from the sources Windows is allowed to use, the repair can fail with 0x800F081F.
Why can DISM show this error?
DISM — Deployment Image Servicing and Management — can inspect and repair the Windows component store.
A common repair command is:
DISM.exe /Online /Cleanup-Image /RestoreHealth
Microsoft states that RestoreHealth scans for component-store corruption and performs repair operations automatically. [R4]
When no explicit source is supplied, Windows can use the repair source configured by policy and, for online images, Windows Update. [R4]
If DISM cannot obtain the files it needs, it may itself return 0x800F081F.
In that situation, repeatedly running the same command without changing the available repair source may produce the same result.
Why might Windows Update not provide the files?
Several different conditions can lead to the same source-missing result.
For example:
- Windows Update is unavailable to the repair process;
- organizational policy tells Windows to use another repair source;
- the configured repair source does not contain the needed files;
- the source image is unsuitable for the installed Windows version or servicing level; or
- the required feature payload is not present in the specified source. [R2] [R3]
The code itself does not identify which of these conditions applies.
That should be determined from the surrounding Windows Update, DISM, policy, and system evidence.
What if I already have Windows installation media?
Installation media can sometimes provide the missing files, but any Windows image is not automatically a valid repair source.
Microsoft warns that the repair source must contain the files required by the target installation. It also recommends keeping a repair source current with servicing updates, because repair can fail when the target Windows installation needs newer files that are absent from the source. [R2]
Language components can matter as well: Microsoft notes that the relevant language packs must be present for supported locales when repairing or restoring features. [R2]
Do not download individual DLLs or other Windows system files from third-party websites to satisfy a missing-source error.
Use Microsoft-provided installation media or another trusted, correctly matched Windows source.
What if this happens while installing .NET Framework 3.5 or another optional feature?
0x800F081F can also occur when Windows is enabling a feature whose payload is not stored locally.
For .NET Framework 3.5, Microsoft explicitly defines 0x800F081F as “The source files could not be found” and instructs administrators to point the source to the files required for the feature. [R5]
This is slightly different from an ordinary cumulative-update failure, even though the same code appears.
The surrounding operation therefore matters:
- Windows Update / component repair → investigate the Windows component store and permitted repair source.
- Optional feature installation → confirm that the source actually contains that feature's payload.
Could company policy cause this?
Yes.
Windows supports Group Policy settings that control where optional component and repair content comes from.
An organization can specify an alternate source and can also prevent the computer from downloading repair content directly from Windows Update. [R2] [R3]
On a work or school PC, do not override these settings yourself merely to make the error disappear.
If the machine is managed, the correct repair source may be maintained by the organization's administrator.
What should I do now?
- Note which update, repair, or optional-feature operation produced
0x800F081F. - If Windows Update itself is otherwise working, retry the original operation once after restarting the PC.
- If component corruption is being repaired, run the supported DISM RestoreHealth workflow.
- If DISM also returns
0x800F081F, treat that as evidence that its required repair files were not available. - Check whether Windows Update is permitted and reachable as a repair source.
- On a managed PC, check with the administrator before changing repair-source or Group Policy settings.
- If an alternate source is required, use a trusted Windows source that matches the installed system closely enough to contain the needed files.
- After DISM repairs the component store successfully, run System File Checker (
sfc /scannow) as recommended by Microsoft for Windows Update corruption cases. [R1] - Restart Windows and retry the original update or feature installation.
See also: windows-update-error-0x80073712
A successful repair means Windows obtains the required source files, completes the repair or feature operation, and the original Windows Update operation succeeds.
Pointing DISM at a different folder without a successful repair result is not by itself proof that the incident is resolved.