Services fail to authenticate: /lib64/libpam.so.0: version `LIBPAM_MODUTIL_1.1.9' not found

Issue

• On RHEL7 with ELS subscription. After installing pam-1.1.8-23.el7_9.1 to rectify the issue described in CVE-2025-6020, various services fail to authenticate with below error:

  PAM unable to dlopen(/usr/lib64/security/pam_unix.so): /lib64/libpam.so.0: version `LIBPAM_MODUTIL_1.1.9' not found (required by /usr/lib64/security/pam_unix.so)
  

• For example, saslauthd recorded below error in /var/log/secure:

  saslauthd[6083]: PAM unable to dlopen(/usr/lib64/security/pam_unix.so): /lib64/libpam.so.0: version `LIBPAM_MODUTIL_1.1.9' not found (required by /usr/lib64/security/pam_unix.so)
  saslauthd[6083]: PAM adding faulty module: /usr/lib64/security/pam_unix.so
  saslauthd[6083]: PAM unable to dlopen(/usr/lib64/security/pam_namespace.so): /lib64/libpam.so.0: version `LIBPAM_MODUTIL_1.1.9' not found (required by /usr/lib64/security/pam_namespace.so)
  saslauthd[6083]: PAM adding faulty module: /usr/lib64/security/pam_namespace.so
  

• atd:

  atd[9201]: PAM unable to dlopen(/usr/lib64/security/pam_unix.so): /lib64/libpam.so.0: version `LIBPAM_MODUTIL_1.1.9' not found (required by /usr/lib64/security/pam_unix.so)
  atd[9201]: PAM adding faulty module: /usr/lib64/security/pam_unix.so
  

• vsftpd:

  vsftpd[764]: PAM unable to dlopen(/usr/lib64/security/pam_unix.so): /lib64/libpam.so.0: version `LIBPAM_MODUTIL_1.1.9' not found (required by /usr/lib64/security/pam_unix.so)
  vsftpd[764]: PAM adding faulty module: /usr/lib64/security/pam_unix.so