Affected versions of this crate did not prevent deep recursion while
deserializing data structures.
This allows an attacker to make a YAML file with deeply nested structures
that causes an abort while deserializing it.
The flaw was corrected by checking the recursion depth.
clap 2.33 is not affected by this because it uses
in a way that doesn't trigger the vulnerability. More specifically:
The input to the YAML parser is always trusted - is included at compile
The nesting level is never deep enough to trigger the overflow in practice
(at most 5).