Exception has been thrown by the target of an invocation

[an2508374]

What type of issue is this?

Question

What SharePoint development model, framework, SDK or API is this about?

SharePoint REST API

Target SharePoint environment

SharePoint Online

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

Request is done using Application Permissions.

Issue description

When executing SharePoint REST API requests to enumerate list items (in our case: getting the last item ID for a list/drive), sometimes we receive the following error:

Request (example):

GET https://<tenant>.sharepoint.com/sites/<site>/_api/web/lists/GetById('<list-guid>')/items?$orderby=Id desc&$select=Id&$top=1

Response:

Status: 500 Internal Server Error
ErrorCode: "-1, System.Configuration.ConfigurationErrorsException"
Error Message: "Exception has been thrown by the target of an invocation. (C:\\inetpub\\wwwroot\\wss\\VirtualDirectories\\80\\web.config line 909)"

Observed in production logs:

• A few independent examples (different tenants, sites, drives), which are getting affected by this issue, show the same exception type and the same web.config line reference.
• This error is usually temporary for affected tenants, but everyday we can find a few another tenants which are experiencing this issue.

Another observations:

• The request is read-only and quite simple ($top=1, orderby Id desc, select Id) — yet the server returns a configuration exception.
• The error message references a server-side file path:
  C:\inetpub\wwwroot\wss\VirtualDirectories\80\web.config line 909
  which suggests this failure originates inside SharePoint/IIS hosting infrastructure, not from client payload/formatting.
• Because the failure happens against SharePoint Online tenants, we cannot inspect or fix the referenced web.config (server-owned).
• The error appears intermittently: the same operation may succeed at other times for the same tenant/list.

Questions:

• Is this error by design (e.g., a transient infrastructure failure surfaced as 500)?
• What is the actual root cause behind:
  System.Configuration.ConfigurationErrorsException pointing to web.config line 909?
• Is there a recommended client-side handling strategy besides retries (e.g., specific headers, correlation IDs, or backoff rules)?

[Ashlesha-MSFT]

Hello @an2508374,
Thank you for bringing this issue to our attention. We will look into it and get back to you shortly.
If you don’t receive a reply within two working days, please use this escalation form to escalate.

[Ashlesha-MSFT]

@an2508374,

I tested the same GET request on a SharePoint Online tenant and received a correct 200 response — unable to reproduce the 500 error on demand, which confirms this is an intermittent server-side/infrastructure issue on Microsoft's end, not a client-side problem.

Since this originates from SharePoint Online's internal IIS configuration (web.config line 909) which is outside the scope of what can be addressed via this repo, I'd recommend:

Raise a Microsoft Support ticket directly via Microsoft 365 Admin Center→ Support → New service request, referencing this GitHub issue
Include in your ticket:

• The full error response body
• The request-id response header value from a failed request
• The x-ms-diagnostics response header value
• Affected tenant names/URLs and approximate timestamps of failures

These correlation IDs will allow Microsoft's support engineers to trace the exact server-side failure in their infrastructure logs — something that cannot be investigated through this GitHub repo alone.