curl shows error on Plesk server: Could not resolve host: example.com: Name or service not known

Symptoms 

• cURL utility does not work on the Plesk server.

• Other tools are able to resolve the hostname properly.

• Unable to open PHP page that uses cURL:

  Could not resolve host: example.com: Name or service not known

• CentOS/RHEL was upgraded to the newer version

• OpenSSL packages were updated recently:

  # grep -i ssl /var/log/yum.log
  Updated: 1:openssl-libs-1.0.2k-12.el7.x86_64
  Updated: 1:openssl-1.0.2k-12.el7.x86_64

• glibc package was updated recently:

  # grep -i glibc /var/log/yum.log
  Updated: 1:glibc-2.17-196.el7_4.2.x86_64
  Updated: 1

• Cannot issue Let's Encrypt certificate:

  ERR [extension/letsencrypt] Domain validation failed: Could not obtain directory: cURL error 6: Could not resolve host: acme-v01.api.letsencrypt.org; Name or service not known 

• Plesk license cannot be updated:

  license server https://id-00.kaid.plesk.com:443/ (): Couldn't resolve host name(6) cURL cannot communicate with license server https://id-00.kaid.plesk.com:443/ (): Couldn't resolve host name(6) (Error code: 2)

• Unable to add domains to Cloudflare with Cloudflare ServerShield extension.

• Unable to install a license key in Tools & Settings > License Management > Install Key. Following error message appears in Plesk interface:

  Error: cURL cannot communicate with license server https://id-00.kaid.plesk.com:5224/ (): Couldn't resolve host name(6) cURL cannot communicate with license server https://id-00.kaid.plesk.com:5224/ (): Couldn't resolve host name(6)

• In some cases license can be successfully installed via CLI with the following command:

  # plesk bin license -i AAAAA-BBBBB-CCCCC-DDDDD-EEEEE

Cause

Shared libraries used by curl were updated, for example: OpenSSL, glibc.

Resolution

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