When trying below curl command for SSL cert, error occurred:
[test@host1 ~]$ curl -v -X GET -u user:pass https://example.com/v1/api.sh
* About to connect() to example.com port 443 (#0)
* Trying 192.168.247.61... connected
* Connected to example.com (192.168.247.61) port 443 (#0)
* Initializing NSS with certpath: sql:/etc/pki/nssdb
* CAfile: /etc/pki/tls/certs/ca-bundle.crt
* Remote Certificate has expired.
* NSS error -8181
* Closing connection #0
* Peer certificate cannot be authenticated with known CA certificates
curl: (60) Peer certificate cannot be authenticated with known CA certificates
More details here: http://curl.haxx.se/docs/sslcerts.html
curl performs SSL certificate verification by default, using a "bundle"
of Certificate Authority (CA) public keys (CA certs). If the default
bundle file isn't adequate, you can specify an alternate file
using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
the bundle, the certificate verification probably failed due to a
problem with the certificate (it might be expired, or the name might
not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
the -k (or --insecure) option.
However, the cert had not expired (it's Aug 2018):
[test@host1 ~]# echo | openssl s_client -connect example.com:443 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' | openssl x509 -noout -dates
depth=2 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert Global Root CA
depth=1 C = US, O = DigiCert Inc, CN = DigiCert SHA2 Secure Server CA
depth=0 C = US, ST = California, L = Redwood City, O = Oracle Corporation, OU = Oracle OCI SALT-LAKE-CITY, CN = example.com
notBefore=Dec 13 00:00:00 2017 GMT
notAfter=Dec 13 12:00:00 2018 GMT
After some debugging, it's found the system date was "2000", and after setting the correct system time to 2018, the issue got resolved.