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Proxy Server and IE9 Windows 7 – Certificate Error

March 5, 2012


You access HTTPS websites while using a proxy (Squid 3.1) and get a Certificate Error.  You get the error because the WINHTTP process cannot authenticate with the proxy server. WINHTTP is making  a Certificate lookup request to a CA.


  1. Lunch the Event Viewer -> Applications and Service Logs -> Microsoft -> Windows -> CAPI2 -> Right-click Operational  and Enable Log,
  2. Open the HTTPS website that is giving certificate error,
  3. Go back to the Event Viewer,
  4. Check which CA WINHTTP is trying to reach,
  5. Lookup the CAs IP range.


  1. Go to the proxy server,
  2. Set the IP range of the CA to no authentication with a filter exception.

From → Security, Windows 7

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