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Fixing SSH Login Failure Due to Missing pam_imunify.so on CloudLinux Servers

The Problem

On one of our CloudLinux servers (bdvip1), we encountered a strange SSH issue:

  • Root password was correct.

  • sshd_config had PasswordAuthentication yes and PermitRootLogin yes.

  • Still, SSH login was failing repeatedly with “Permission denied”, even though the credentials were correct.

SSH Debug Output

Running SSH in verbose mode:

ssh -vvv root@160.191.128.XXX

Showed this:

debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
...
debug1: Next authentication method: password
root@160.191.128.XXX's password:
Permission denied

Root Cause: pam_imunify.so Was Missing

Upon checking system logs:

journalctl -xe | grep sshd

We found this error:

PAM unable to dlopen(/usr/lib64/security/pam_imunify.so): No such file or directory
PAM adding faulty module: /usr/lib64/security/pam_imunify.so

What Is pam_imunify.so?

pam_imunify.so is a PAM (Pluggable Authentication Module) used by Imunify360 to monitor login attempts and enforce security controls.

However, in our case:

  • Imunify360 was removed or not installed properly, so

  • the PAM module pam_imunify.so no longer existed on the server,

  • but the PAM configuration files still referenced it.

This caused PAM authentication to fail for all logins, including SSH—even though the password was correct.

 The Fix

Step 1: Remove All References to pam_imunify.so

Edit or clean up the following files:

sed -i '/pam_imunify.so/d' /etc/pam.d/system-auth
sed -i '/pam_imunify.so/d' /etc/pam.d/password-auth

This removes the broken authentication lines:

auth required pam_imunify.so
auth required pam_imunify.so check_only

These two files are included by almost all login systems (SSH, sudo, console login). If they’re misconfigured, no login will work.

Step 2: Restart SSH

systemctl restart sshd

Step 3: Test SSH Again

ssh root@<your-server-ip>

Now the login should work using your root password.

Optional: Want to Reinstall Imunify360?

If you still want to use Imunify360 and its login protection features:

wget https://repo.imunify360.cloudlinux.com/defence360/i360deploy.sh
bash i360deploy.sh

This will properly reinstall Imunify360 and restore the pam_imunify.so module.

 Conclusion

This issue was caused by leftover PAM configuration after a partial or broken removal of Imunify360. It shows how sensitive PAM configurations are—even a single missing module can block all logins.

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