Vulnerability Instance

Possible DoS Vulnerability in Active Record PostgreSQL adapter
There is a possible DoS vulnerability in the PostgreSQL adapter in Active
Record. This vulnerability has been assigned the CVE identifier CVE-2021-22880.

Versions Affected:  >= 4.2.0
Not affected:       < 4.2.0
Fixed Versions:     6.1.2.1, 6.0.3.5, 5.2.4.5

Impact
------
Carefully crafted input can cause the input validation in the "money" type of
the PostgreSQL adapter in Active Record to spend too much time in a regular
expression, resulting in the potential for a DoS attack.

This only impacts Rails applications that are using PostgreSQL along with
money type columns that take user input.

Workarounds
-----------
In the case a patch can't be applied, the following monkey patch can be used
in an initializer:

```
module ActiveRecord
  module ConnectionAdapters
    module PostgreSQL
      module OID # :nodoc:
        class Money < Type::Decimal # :nodoc:
          def cast_value(value)
            return value unless ::String === value

            value = value.sub(/^\((.+)\)$/, '-\1') # (4)
            case value
            when /^-?\D*+[\d,]+\.\d{2}$/  # (1)
              value.gsub!(/[^-\d.]/, "")
            when /^-?\D*+[\d.]+,\d{2}$/  # (2)
              value.gsub!(/[^-\d,]/, "").sub!(/,/, ".")
            end

            super(value)
          end
        end
      end
    end
  end
end
```