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Firefox shows Errror Code "ssl_error_bad_mac_read" when trying to access Secure Sites


When I try to access secures sites (URLs with https) Firefox shows me the error code "ssl_error_bad_mac_read".

This problem only appears in Firefox not in Internet Explorer and it also appears when I use Firefox in Secure Mode. The problem appeared this morning for the first time, until yesterday everything worked fine and I didn't install or update any new PlugIns, Addons, Firewalls or something like that.

I tried to make the SSL-Test from Boston University you propose on your help page and couldn't access that page either. I use Firefox with the version 5.0 and would be glad to receive any hint to solve the problem.

Modified by k_a_r_o_l_a

Additional System Details

Sites Affected


Installed Plug-ins

  • BitDefender QuickScan Web Netscape Plugin
  • Zylom Plugin
  • RealPlayer(tm) LiveConnect-Enabled Plug-In
  • RealJukebox Netscape Plugin
  • The QuickTime Plugin allows you to view a wide variety of multimedia content in Web pages. For more information, visit the QuickTime Web site.
  • npdivxplayerplugin
  • getplusplusadobe16263
  • NPRuntime Script Plug-in Library for Java(TM) Deploy
  • Adobe PDF Plug-In For Firefox and Netscape 10.1.0
  • Shockwave Flash 10.3 r181
  • DivX Web Player version
  • GEPlugin
  • Next Generation Java Plug-in 1.6.0_24 for Mozilla browsers
  • Panda ActiveScan 2.0 Plugin for Firefox
  • Npdsplay dll


  • User Agent: Mozilla/5.0 (Windows NT 5.1; rv:5.0) Gecko/20100101 Firefox/5.0

More Information

Hasan 477 solutions 5600 answers

Helpful Reply

Open Firefox -> go to Tools Menu -> Options -> Advanced -> Encryption -> Protocols section -> Put Checkmarks on both options -> Certificates section-> select Radio Button Option 2 -> Click OK.

Helpful Reply

Thanks for your help, but exactly all of these options have already been checked.

Hasan 477 solutions 5600 answers

- Open Firefox -> got to Help Menu -> select "Restart with Add-ons Disabled"

Firefox will close then it will open up with just basic Firefox. You can enable the Add-ons later. Check if its working.

Question owner

Thanks for the hint, but since this afternoon the matter seemed to have resolved itself. Without having anything changed I could access secure sites with Firefox.

But given the fact that I have found several similar (unsolved) problem definitions in other forums where the people told that the problem appeared once again from time to time, I will keep your hint in mind and will check if it'll help in case it happens again.