FIX: "Error HTTP 503: The Service is unavailable" error when the connection to the UAG trunk fails in Forefront Unified Access Gateway 2010 Service Pack 4

Applies to: Microsoft Forefront Unified Access Gateway 2010 Service Pack 4

Symptoms


Client connections to the Microsoft Forefront Unified Access Gateway (UAG) 2010 Service Pack 4 (SP4) trunk for published applications may fail, and the client receives the following error message:

Error HTTP 503

The Service is unavailable.


Additionally, you may find intermittently logged Application log errors that are related to an application fault for Internet Information Services (IIS) worker process. These errors resemble the following:

Faulting application name: w3wp.exe, version: 7.5.7601.17514, time stamp: 0x01234567
Faulting module name: KERNELBASE.dll, version: 6.1.7601.18409, time stamp: 0x76543210
Exception code: 0xc0000005
Fault offset: 0x000000000000940d
Faulting process id: 0x1234
Faulting application path: c:\windows\system32\inetsrv\w3wp.exe
Faulting module path: C:\WINDOWS\system32\KERNELBASE.dll

Cause


This problem occurs because of incorrect connection handling in the UAG Whlfilter.dll file.

Status


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

References


Learn about the terminology that Microsoft uses to describe software updates.