Possible Remote Code Execution Exploit in Rails Development Mode

There is a possible a possible remote code executing exploit in Rails when in
development mode. This vulnerability has been assigned the CVE identifier
CVE-2019-5420.

Versions Affected: 6.0.0.X, 5.2.X.
Not affected: < 5.2.0
Fixed Versions: 6.0.0.beta3, 5.2.2.1

Impact

With some knowledge of a target application it is possible for an attacker to
guess the automatically generated development mode secret token. This secret
token can be used in combination with other Rails internals to escalate to a
remote code execution exploit.

All users running an affected release should either upgrade or use one of the
workarounds immediately.

Releases

The 6.0.0.beta3 and 5.2.2.1 releases are available at the normal locations.

Workarounds

This issue can be mitigated by specifying a secret key in development mode.
In “config/environments/development.rb” add this:

config.secret_key_base = SecureRandom.hex(64)

Credits

Thanks to ooooooo_q