Chef Progress has already begun working on a fix that will be released in the next Chef Infra Server release, see: chef/chef-server#2992
If for some reason you can't upgrade soon here is an alternative. I highly recommend upgrading instead of using this fix. This fix is meant to be a stop gap solution.
This only works if you're using a version of Chef Infra Server that ships with elasticsearch. If you're using an old version of Chef Infra Server that is still using solr this won't work.
Quickly validate that you're using a moden version of Chef Infra Server:
sudo ps -ef | grep -i elastic
If you see an elasticsearch process than this fix will most likley work for you.
If you're running an older version of Chef Infra Server you might not even be effected by the vulnerability because the solr instance uses log4j 1.x which, according to some articles, doesn't have the vulnerability.