I'm unable to reproduce reported issue with latest Tumbleweed nor SLE15 SP4. Can you please try on machine where you are using lftp client following command: > openssl verify <your_vstpd_cert.pem> You should receive something like this: > cert.pem: OK But I guess you will receive following error: > error 18 at 0 depth lookup: self signed certificate > error cert.pem: verification failed This means you need to install your certificate into trust storage. Simply copy your certificate into: > /usr/share/pki/trust/anchors/ and run > update-ca-certificates Then openssl verification should return "OK" and also lftp command should no longer complain. Anyway, I see your Tumbleweed is quite outdated, I recommend to update your system before reporting issue. Especially in OpenSSL there was a big change - we changed default version from 1.1 to 3.0 and all Tumbleweed packages are build against this new version. Please let me know it your problem is resolved.