WHMCS has discovered a problem in an earlier EA4 Curl Package introduced on CentOS servers.
UPDATE: This is reportedly fixed in ea-libcurl-7.67.0-2.2.1, so it should no longer be necessary to downgrade.
Per https://forums.cpanel.net/threads/cpanel-curl-update-breaks-whmcs-enom-module.663449/ it may be necessary to restart PHP-FPM to apply the changes to the running PHP binaries.
You may receive the error seen below when trying to accomplish certain activities on remote systems, like trying to register a domain via eNom, managing a domain, or other hosting activities related to the accounts on your server.
CURL Error: 56 – OpenSSL SSL_read: Success
According to the curl devs, this issue is caused by:
an increase in the sensitivity of OpenSSL’s SSL_ERROR_SYSCALL error so that abrupt server closures are also considered errors.https://lqwb.us/2QGVZCH
Evidently, when a server does not send a recognized ‘protocol termination point’ (eg. a HTTP content length or a zero length chunk and empty trailer) it will cause an error if the connection is closed abruptly. The absence of a TLS termination point (eg. a close_notify alert) will highlight this problem and increase the chances of this error occurring. This concern can also affect additional versions of CURL which utilize API system calls.
The previous system update to cURL 7.67 in EasyApache 4 version 2019-11-20 includes changes which caused this problem. The issue has been identified by the cURL developers and will be addressed in upcoming updates.
In order to address this issue right now, reverting to a prior version of cURL (version 7.66) will resolve the error:
[root@host]# yum downgrade ea-libcurl ea-libcurl-devel
We should also note that the WHMCS technical support team is unable to assist with this issue as it is a result of an upstream bug in curl.