Error: 431 Request Header Fields Too Large

prokrishnaa1 says:

<add header="Content-type" sizeLimit="100" />

Your setting doesn't allow HTTP requests where the length of the "Content-type" header is greater than 100 bytes.

For increasing the Content-Length set the sizeLimit.

<headerLimits>
    <add header="Content-type" sizeLimit="1000" />
</headerLimits>

It allows the Content-Length with 1000 bytes.

<add header="Content-type" sizeLimit="100" /> we should not increase the size... its a VA issue. suggest how to customise the header request length

sizeLimit="100" 

Hi dharmendra das, Thanks for response. if i have change the length then its will work. But As part of the VA should be sizeLimit="100"  only... Please advise how to customie the header length to fix the issue.

Content-Length: 2717 Content-Type: multipart/related; type="application/xop+xml";start="<http://tempuri.org/8>"; boundary="uuid:28cb7499-e6c0-4820-281-897966f41f53-10-2" start info="application/soap+xml" Accept-Encoding: gzip, deflate Expect: 100-continue

above bold text coming arrount 184 char, if i have mentioned more than above length its working other wise it will give 431 error will come. Please advide customise Content-Type to fix this issue with <add header="Content-type" sizeLimit="100" />

Hi prokrishnaa1,

You can set the Content-type sizeLimit from code behind.

C#

using (ServerManager serverManager = new ServerManager())
{
    Configuration config = serverManager.GetWebConfiguration("Default Web Site");
    ConfigurationSection requestFilteringSection = config.GetSection("system.webServer/security/requestFiltering");
    ConfigurationElement requestLimitsElement = requestFilteringSection.GetChildElement("requestLimits");
    ConfigurationElementCollection headerLimitsCollection = requestLimitsElement.GetCollection("headerLimits");

    ConfigurationElement addElement = headerLimitsCollection.CreateElement("add");
    addElement["header"] = @"Content-type";
    addElement["sizeLimit"] = 10000;
    headerLimitsCollection.Add(addElement);

    serverManager.CommitChanges();
}

VB.Net

Dim serverManager As ServerManager = New ServerManager
Dim config As Configuration = serverManager.GetWebConfiguration("Default Web Site")
Dim requestFilteringSection As ConfigurationSection = config.GetSection("system.webServer/security/requestFiltering")
Dim requestLimitsElement As ConfigurationElement = requestFilteringSection.GetChildElement("requestLimits")
Dim headerLimitsCollection As ConfigurationElementCollection = requestLimitsElement.GetCollection("headerLimits")

Dim addElement As ConfigurationElement = headerLimitsCollection.CreateElement("add")
addElement("header") = "Content-type"
addElement("sizeLimit") = 10000
headerLimitsCollection.Add(addElement)

serverManager.CommitChanges()

Reference:

https://learn.microsoft.com/en-us/iis/configuration/system.webserver/security/requestfiltering/requestlimits/headerlimits/