Shibboleth SP3 Problem: xmltooling::IOException setHeader (Header) failed: -2147024809

Stephen Holland-Chang stephen at
Thu Jan 21 21:39:26 UTC 2021

We increased the IIS HTTP Registry setting for MaxRequestBytes and MaxFieldLength hoping it was a problem with the HTTT request header length
see :

But that DID NOT fix the issue. 

Does anyone know if there is a way we can debug the error and figure out which actual attribute is throwing the setHeader Failed error? 
We can see the data in the Shibboleth log but the error is thrown elsewhere I expect IIS API? 
The IIS logs do not show any error though. If we can isolate the attributes causing the error we can figure out going on.

We do know that the 2 users having the problem have one attribute “role” which has (71 values) and wondering if that causing the problem since most of the other users only have 1-6 values. Thats the only field that looks particularly distinctive.

Thanks for any help.

> On Jan 14, 2021, at 5:13 PM, Cantor, Scott <cantor.2 at> wrote:
> On 1/14/21, 8:11 PM, "users on behalf of Stephen Holland-Chang" <users-bounces at on behalf of stephen at> wrote:
>>   Ah ok thanks, looking at the data closer, I believe the issue could be with the length of the attribute values as they are
>> quite long.
> That is the most obvious risk, but how long are we talking? That is not a normal thing for an IdP to do.
>> I increased the Content-Length of IIS Request Filtering to allow for larger headers and will see if that does the trick. 
> Can you outline where/what setting it is so I can document it?
> -- Scott
> -- 
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