Policy

Set maximum Kerberos SSPI context token buffer size

Windows 11 25H2

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Policy overview

Key metadata and intent for this policy.

ClassComputer
CategorySystem > Kerberos
Supported onAt least Windows Server 2003 operating systems or Windows XP Professional

Supported OS tags: Windows10, Windows10RT, Windows11, Windows7, Windows8, Windows81, WindowsRT, WindowsRT81, WindowsServer2003, WindowsServer2008, WindowsServer2012, WindowsServer2012R2, WindowsServer2016, WindowsVista, WindowsXP

This policy setting allows you to set the value returned to applications which request the maximum size of the SSPI context token buffer size. The size of the context token buffer determines the maximum size of SSPI context tokens an application expects and allocates. Depending upon authentication request processing and group memberships, the buffer might be smaller than the actual size of the SSPI context token. If you enable this policy setting, the Kerberos client or server uses the configured value, or the locally allowed maximum value, whichever is smaller. If you disable or do not configure this policy setting, the Kerberos client or server uses the locally configured value or the default value. Note: This policy setting configures the existing MaxTokenSize registry value in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters, which was added in Windows XP and Windows Server 2003, with a default value of 12,000 bytes. Beginning with Windows 8 the default is 48,000 bytes. Due to HTTP's base64 encoding of authentication context tokens, it is not advised to set this value more than 48,000 bytes.

Internal name
MaxTokenSize
Policy ID
8779fabd0c9f
Elements
1

Registry values

How enabled and disabled states update the registry.

Registry locationTypeEnabled valueDisabled value
HKLM\System\CurrentControlSet\Control\Lsa\Kerberos\Parameters\EnableMaxTokenSizeREG_DWORD
1
0

Policy elements

Inputs and configuration options exposed by this policy.

ElementTypeRegistry mappingConstraints & behavior
Maximum size
ID MaxTokenSize
decimal
HKLM\System\CurrentControlSet\Control\Lsa\Kerberos\Parameters\MaxTokenSize
Type REG_DWORD
Range: 12000 to 2147483647

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