In newer passenger versions the output of passenger -v has changed. capistrano-passenger tries to parse the version and now causes the error undefined method '[]' for nil:NilClass. To fix this you only need to upgrade the capistrano-passenger gem.

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

• Prevents you from data breaches and liability risks
• Upgrade at your own pace
• Works with modern Rubies

Read more Show archive.org snapshot

Therefore run bundle update capistrano-passenger --conservative.

The version change of passenger from 6.0.7 to 6.0.8 has triggered this problem. This is fixed in capistrano-passenger >= 0.2.1.