500 error after SharePoint Cumulative Update

Question

We have a SharePoint on-premise 2016 environment with 3 WFE and 3 APP servers. After the December 2022 cumulative update, we had no issues, and the sites were running fine. However, after installing the February 2023 cumulative update, we started experiencing a 500 internal error. With every subsequent cumulative update, this issue recurs, and we have to replace the updated web.config file with the old one from the December 2022 update. Using the old web.config file resolves the issue.We have tried checking and comparing the old and new web.config files, but there are so many changes that we're not sure what to look for. Do you have any suggestions?

Answer 1

Hi Lazy Bee,

500 internal error analysis can be frustrating, but you can try this quick checks;

• Insite one server with error, and inside of IIS Manager browse the SharePoint web application where you encounter the error, get a detailed error message to identify the specific issue in the SharePoint Web Config file.
• Check if Web App Pool is stopped, if yes, start it.
• You can also reset IIS.

For forensics analysis, you need check all event logs after your update. can be hard, but can be the way.

Answer 2

Hi @Lazy Bee ,

Thank you for posting in this community.

Per my knowledge, it is possible to use the old version of the web.config file directly, which usually doesn't make much difference. If you want to find a specific problem with the new web.config file, you may need to compare it with the old one, which is usually very time-consuming.

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