Confluence UI shows garbled or corrupt text on CAPTCHA, macros and/or diagrams due to missing fonts in Linux

Macro header shows garbled text and weird symbols in Linux. Captcha appears warped and unreadable.

Environment

1. Linux distributions, especially RedHat (RHEL)  and CentOS
2. Confluence v6 and above

Steps to reproduce

1. Insert any macro having a title, like the Panel Macro

Expected Behavior

Macro header (the name of the macro) renders properly

Actual Behavior

Strange characters appear in place of the macro name.

Workaround

1. Stop Confluence
2. Make one or both of the following changes:
   • Uninstall lyx-fonts package (Lyx/MathML fonts - A collection of Math symbol fonts for lyx) if it is installed on the server
   • Ensure the following fonts are installed:

     yum install ghostscript
     yum install dejavu-fonts-common
     yum install dejavu-sans-fonts
     yum install dejavu-sans-mono-fonts
     yum install motif
     

     some versions of ghostscript package can be affected by security vulnerability CVE-2018-16509 discovered in September 2018.
     for more details see

   • https://security-tracker.debian.org/tracker/CVE-2018-16509
   • https://access.redhat.com/security/cve/cve-2018-16509
   • https://www.exploit-db.com/exploits/45369/
3. Rebuild the font cache by using the following command:

   fc-cache -s
   

4. Clear the plugin cache as described at How to clear Confluence plugins cache
5. Rebuild the content index as described at How to Rebuild the Content Indexes From Scratch on Confluence Server
6. Start Confluence
7. Clear browser cache and verify fonts are displayed correctly

Notes

Confluence requires some fonts to work in Linux distributions that are not included in the installation package or in the documentation as a requirement.

In some cases, the workaround also works for file previews such as Office files and PDF.