Fixing the “For security reasons DTD is prohibited in this XML document.” issue

This post was most recently updated on October 4th, 2022.

This post describes a couple of ways to fix the issue “For security reasons DTD is prohibited in this XML document”. At least for me, it appeared when trying to access SharePoint Online using Powershell or a console program using OfficeDev.PnP (which in turn uses CSOM).

Error

When running any piece of code, whether in PowerShell, .exe console, or anything else than the code behind relies on .NET Framework, you get an error like this:

For security reasons DTD is prohibited in this XML document. To enable DTD processing set the ProhibitDtd property on XmlReaderSettings to false and pass the settings into XmlReader.Create method.

It could come from, for example, running Connect-SPOnline on PowerShell. Ours was first caused by the custom console app, but then also by running Powershell.

Reason for the problem

There are a number of issues that can cause this, and hence there are a few different solutions.

We got the error when we were supposed to provision certain artifacts on SharePoint online using PowerShell, based on an XML document describing the steps – think PnP provisioning templates. This led us to think it was somehow related to the XML file in question. This seemed logical.

However, the error itself just denies the processing of an XML document with DTD and doesn’t tell what this document actually is. Besides, why would a document with a DTD (Document Type Definition, typically used to describe the schema and structure of the document) suddenly become invalid, while it worked just the day before?

Well, of course, because it actually had nothing to do with our implementation!

This happened on multiple different machines, and multiple different network connections, with any XML input, but just against one tenant (others worked) – so we figured it has to be about some configuration on that particular tenant or data center. Furthermore, Connect-SPOService (to admin site) worked, but Connect-SPOnline to normal site failed.

That’s curious, right?

Solutions

Weird issue, but in the end, an easy solution.

 Links and references

• More information about the DNS issues:
  • http://asp.net-hacker.rocks/2016/01/15/XML-parsing-problem-because-of-your-ISP.html
  • https://stackoverflow.com/questions/13854068/dtd-prohibited-in-xml-document-exception
  • https://blogs.technet.microsoft.com/marios_mo_betta_blog/2016/06/05/o365-powershell-error-dtd-is-prohibited-in-this-xml-document/ (this one is about Verizon)
• More info about the IPv6 issues:
  • https://melcher.it/2016/02/for-security-reasons-dtd-is-prohibited-in-this-xml-document/

Normally, I’d make those entries into links, but apparently, Gutenberg (WordPress’s new editor) crashes if I do that, so I’m just not gonna. Sorry!

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Antti K. Koskela

Developer / Speaker / Consultant at Koskila / Precio Fishbone / Norppandalotti Software Co / Alter - Experience Ideas Ltd

Antti Koskela is a proud digital native nomadic millennial full stack developer (is that enough funny buzzwords? That's definitely enough funny buzzwords!), who works as Solutions Architect for Precio Fishbone, building delightful Digital Workplaces.

He's been a developer from 2004 (starting with PHP and Java), and he's been working on .NET projects, Azure, Office 365, SharePoint and a lot of other stuff. He's also Microsoft MVP for Azure.

This is his personal professional (e.g. professional, but definitely personal) blog.

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