При добавлении любого пакета, командой composer require, композер стал валиться с ошибкой:

$ composer require vendor/package

[Composer\Downloader\TransportException]
  The "https://api.github.com/repos/vendor/package" file could not be downloaded: SSL operation failed with code 1. OpenSSL Error messages:
  error:14090086:SSL routines:ssl3_get_server_certificate:certificate verify failed
  Failed to enable crypto
  failed to open stream: operation failed


require [--dev] [--prefer-source] [--prefer-dist] [--no-progress] [--no-suggest] [--no-update] [--no-scripts] [--update-no-dev] [--update-with-dependencies] [--update-with-all-depe
ndencies] [--ignore-platform-reqs] [--prefer-stable] [--prefer-lowest] [--sort-packages] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [--apcu-autoloader] [--] [<package
s>]...

Гуглились в основном решения с указанием файлов сертификатов в php.ini в опциях openssl.cafile и curl.cainfo.

Мне помогло просто обновление самого composer:

composer self-update