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Troubleshoot HTTP 502.2 Bad Gateway error in CGI applications

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Applies to:   Internet Information Services

This article describes HTTP 502.2 Bad Gateway error in Common Gateway Interface (CGI) applications and provides troubleshooting steps to resolve this issue.

Symptom

You have a Web site that is hosted on Internet Information Services (IIS). When you visit the Web site in a Web browser, you might receive an error message that resembles the following one:

Server Error in Application <application name> HTTP Error 502.2 - Bad Gateway HRESULT: 0xC00000FD or 0x00000003 Description of HRESULT: Specified CGI application did not return a complete set of HTTP headers.

Cause

This problem occurs because the CGI process terminates unexpectedly before the CGI process sends a response back to IIS.

Tools

Troubleshooting steps

When sending a request to a CGI application running via IIS, the user is presented with the following error instead of the expected response:

The specified CGI application misbehaved by not returning a complete set of HTTP headers

Capture a Netmon trace. It shows:

HTTP: Response to Client; HTTP/1.1; Status Code = 502 - Bad Gateway
HTTP: Protocol Version =HTTP/1.1
HTTP: Status Code = Bad Gateway
HTTP: Reason =Bad Gateway
HTTP: Content-Length =232
HTTP: Content-Type =text/html
HTTP: Server =Microsoft-IIS/6.0
HTTP: Date =Tue, 23 Aug 2005 20:25:47 GMT
HTTP: Data: Number of data bytes remaining = 232 (0x00E8)
00000: 00 11 BC 3E 62 3C 00 0F 1F 6C 1F E1 08 00 45 00 ..%>b<...l.á..E.
00010: 01 9A EF 40 40 00 80 06 00 00 D8 A2 10 5C 0A C8 .šï@@.&euro;...Ø¢.\.È
00020: 04 15 00 50 55 B1 AA C6 89 52 E7 D6 85 01 50 18 ...PU±ªÆ‰RçÖ….P.
00030: 09 2F F9 67 00 00 48 54 54 50 2F 31 2E 31 20 35 ./ùg..HTTP/1.1 5
00040: 30 32 20 42 61 64 20 47 61 74 65 77 61 79 0D 0A 02 Bad Gateway..
00050: 43 6F 6E 74 65 6E 74 2D 4C 65 6E 67 74 68 3A 20 Content-Length: 
00060: 32 33 32 0D 0A 43 6F 6E 74 65 6E 74 2D 54 79 70 232..Content-Typ
00070: 65 3A 20 74 65 78 74 2F 68 74 6D 6C 0D 0A 53 65 e: text/html..Se
00080: 72 76 65 72 3A 20 4D 69 63 72 6F 73 6F 66 74 2D rver: Microsoft-
00090: 49 49 53 2F 36 2E 30 0D 0A 44 61 74 65 3A 20 54 IIS/6.0..Date: T
000A0: 75 65 2C 20 32 33 20 41 75 67 20 32 30 30 35 20 ue, 23 Aug 2005 
000B0: 32 30 3A 32 35 3A 34 37 20 47 4D 54 0D 0A 0D 0A 20:25:47 GMT....
000C0: 3C 68 74 6D 6C 3E 3C 68 65 61 64 3E 3C 74 69 74 <html><head><tit
000D0: 6C 65 3E 45 72 72 6F 72 3C 2F 74 69 74 6C 65 3E le>Error</title>
000E0: 3C 2F 68 65 61 64 3E 3C 62 6F 64 79 3E 3C 68 65 </head><body><he
000F0: 61 64 3E 3C 74 69 74 6C 65 3E 45 72 72 6F 72 20 ad><title>Error 
00100: 69 6E 20 43 47 49 20 41 70 70 6C 69 63 61 74 69 in CGI Applicati
00110: 6F 6E 3C 2F 74 69 74 6C 65 3E 3C 2F 68 65 61 64 on</title></head
00120: 3E 0A 3C 62 6F 64 79 3E 3C 68 31 3E 43 47 49 20 >.<body><h1>CGI 
00130: 45 72 72 6F 72 3C 2F 68 31 3E 54 68 65 20 73 70 Error</h1>The sp
00140: 65 63 69 66 69 65 64 20 43 47 49 20 61 70 70 6C ecified CGI appl
00150: 69 63 61 74 69 6F 6E 20 6D 69 73 62 65 68 61 76 ication misbehav
00160: 65 64 20 62 79 20 6E 6F 74 20 72 65 74 75 72 6E ed by not return
00170: 69 6E 67 20 61 20 63 6F 6D 70 6C 65 74 65 20 73 ing a complete s
00180: 65 74 20 6F 66 20 48 54 54 50 20 68 65 61 64 65 et of HTTP heade
00190: 72 73 2E 3C 2F 62 6F 64 79 3E 3C 2F 62 6F 64 79 rs.</body></body
001A0: 3E 3C 2F 68 74 6D 6C 3E ></html>

Capture FREB log for the HTTP error message and locate which module is throwing this error message.

Troubleshoot the CGI process executable file to determine why the CGI process terminates unexpectedly. You might have to generate a memory dump file of the CGI process when the access violation occurs.

This problem occurs when the CGI application does exactly what the error suggests, inserting invalid data into the HTTP header values that are sent to IIS as part of its response.