Avast and Firefox SEC_ERROR_UNKNOWN_ISSUER

Avast Free Antivirus / Premium Security
1

Hello,

The Avast caused error SEC_ERROR_UNKNOWN_ISSUER in my Firefox 60.0 (64 bits). The problem resolved after disable https scanning.

Article about problem
https://support.mozilla.org/en-US/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER

2
  • Which Avast…? (Free/Pro/IS/Premier)
  • Which version…?
  • OS…? (32/64 Bit…? - which SP/Build…?)
  • Other security related software installed…?
3

Avast Free 18.4.2338
Windows 10 x64 - 1709 Build 16299.431
Yes, COMODO Firewall.

The article cited include Avast in list of softwares that cause the error in Firefox. The COMODO Firewall not influence.

Thank you!

4
  1. Download Avast Free Antivirus: https://files.avast.com/iavs9x/avast_free_antivirus_setup_offline.exe
  2. Follow instructions: https://www.avast.com/uninstall-utility (Run this tool for all prior installed Avast versions…!!)
  3. Reinstall Avast with the downloaded installer from point 1.
  4. Reboot.
5

I have the same problem with the latest version 18.4.2338 on Windows 10 and Firefox 60.0.
Weird thing is that it is happening after my system runs for a few hours…

6

Are you also running Comodo FW…?

7

Nope, just avast.

8

OK, see if the clean reinstall (Reply #3) helps.

9

Hello,

Thank you! The problem is solved now.

10

I’ll wait, if the problem appear again I return here.

11

You’re welcome.

12

Another problem - avastclear wont open in the safe mode…

13

I had to disable https scanning like the OP.

14

If you think making yourself more vulnerable is a good choice than why not. I on the other hand like to be protected any way I can.

After another reboot it has let me to use that tool.

Reinstalled the program and now Firefox crashes cause Avast cant install its addon; it shows problems with email account certificates (all 5 email accounts on different sites), my scanning jobs are gone and instead shows this on the scanning options:
And those are just the things I have noticed right away.

15

Please stay on topic, else start your own thread.

16

SEC_ERROR_UNKNOWN_ISSUER error still occurs after re-install…
Any ideas?

17
  • Which Avast…? (Free/Pro/IS/Premier)
  • Which version…?
  • OS…? (32/64 Bit…? - which SP/Build…?)
  • Other security related software installed…?
  • Which AV(s) did you use before Avast…?
18

Same as 3 days ago: Avast 18.4.2338, Windows 10 64, no other security related programs.

19

Wait for one of the guys with W10, can’t reproduce it here.

20

Ok, Still waiting…