[CVE-2021-22880] Possible DoS Vulnerability in Active Record PostgreSQL adapter

Security Announcements
1

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.

Releases

The fixed releases are available at the normal locations.

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

Patches

To aid users who aren’t able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset.

Please note that only the 5.2, 6.0, and 6.1 series are supported at present. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases.

Credits

Thanks to @dee-see from HackerOne for reporting this issue!

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