After installing July 2026 CU you might experience the issue that Office Online Server will fail to show Office and PDF documents.
The issue is typically reflected in the ULS logs with entries similar to the following:
w3wp.exe (0xXXXX) SharePoint Foundation Claims Authentication ahds5 Unexpected SPJsonWebSecurityBaseTokenHandler: ValidateTokenIssuer rejected Issuer '00000003-0000-0ff1-ce00-000000000000@...random-guid...' because no registered STS matches the signing certificate 'CN=SharePoint Security Token Service, OU=SharePoint, O=Microsoft, C=US'
Solution
A fix for this issue has been released with August 2026 CU for SharePoint Server 2016 which resolves this issue.
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Hi,
we’re experiencing very similar OOS issues after installing the CU July 2026 CU, but in our case the affected environment is running SharePoint Subscription Edition. Users receive errors susch as “You do not have permissions t open the file in the browser” and “No longer connected to the Server” . Does the August 2026 CU for Shp SE also include a fix for the OOS integration issue?
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Hi Marcij,
only SP2016 was affected by the problem outlined in this article.
The issue you are running into is something else – e.g. I would expect that there are no ahds5 events in the SPSE event log.
My recommendation would be to review the ULS log for more details when the problem occurs and if required open a support case with Microsoft to get assistance with this issue.
Cheers,
Stefan
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Hi Stefan,
We have installed the Aug 2026 CU (KB 5002893) on our SPSE farm, and we are having issues with OOS – users attempting to open office documents in the web view are getting errors like
“Sorry, there was a problem and we can’t open this document. if this happens again, try opening the document in Microsoft Word”.
Do we need to run below script?
$farm = Get-SPFarm
$farm.DisableActorTokenAudienceValidation = $true #disables only the defense-in-depth validation
$farm.update()
FYI i haven’t applied OOS patch (KB 5002895) yet.
Could you please advise if there is any fix or workaround to resolve the problem?
Thank you for your assistance