Problem

Following a Confluence upgrade running on an older Linux distribution, you might encounter a problem where certain system text in the application will appear to be garbled and look like symbols instead of regular alphanumeric letters.

You will not see any errors in the logs relating to the issue, however, you might see warnings about fonts in general. 

This has been observed in the following areas of Confluence

CAPTCHA

Macro headers

Inline charts and diagrams

Imported Microsoft Word Documents

Diagnosis

In order to identify whether you are affected by this issue, you will need to answer the below questions:

• Did you upgrade Confluence Server recently to a new version?
• Are you running an older version of a Linux distribution that is behind current release cycle (possibly more than 3+ years old)?

Cause

If you answered yes to both of the above questions, you might be missing fonts on the OS level that more recent versions of Confluence depend on to render pages properly. Bug report for reference:  CONFSERVER-54067 - Getting issue details... STATUS

Resolution

Resolution 1

Uninstall lyx-fonts package (Lyx/MathML fonts - A collection of Math symbol fonts for lyx)

Resolution 2

You will need to check and install the following font packages. You can use any package manager you like. For this example, we will be using yum

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

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/

In order for Confluence to pick up the changes, please apply the below steps:

1. Stop Confluence

2. Rebuild the font cache by using the following command:

   fc-cache -s

3. Clear the Confluence Plugins Cache.
4. Perform a Content Index Rebuild.
5. Start Confluence.
6. Clear your browser cache and verify Confluence is presenting the text properly.
7. If you still see garbled text, try rebooting the server, then check again.