Unbounded exponent in decimal enables unauthenticated DoS

Summary

Uncontrolled Resource Consumption vulnerability in ericmj decimal allows unauthenticated remote Denial of Service. The decimal library does not bound the exponent on parsed input. Storing a decimal with a very large exponent (e.g. Decimal.new("1e1000000000")) is accepted without error. Subsequent calls to arithmetic functions (Decimal.add/2, Decimal.sub/2, Decimal.div/2M), Decimal.to_string/2M with :normalM or :xsdM format, Decimal.to_integer/1M, Decimal.round/3M, or Decimal.compare/3M with a threshold allocate memory proportional to the exponent value, which can exhaust available memory and crash the BEAM VM. Any application that accepts user-supplied decimal input and subsequently performs arithmetic, rounding, conversion to integer, or string formatting on it is exposed. A single malicious request is sufficient to cause an out-of-memory crash. This issue affects decimal: from 0.1.0 before 3.0.0.