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. Note: `clap 2.33` is not affected by this because it uses `yaml-rust` in a way that doesn't trigger the vulnerability. More specifically: 1. The input to the YAML parser is always trusted - is included at compile time via `include_str!`. 2. The nesting level is never deep enough to trigger the overflow in practice (at most 5).