Looked into 4 reported vulnerabilities for libyaml (as they could affect YAML::LibYAML). It turned out it was about two types of vulnerabilities (timeout, memory leak), but libyaml itself was fine. The fuzztesting code had mistakes and they have been fixed by my two PRs 1184811840. So in the end there was no vulnerability, I learned some C and we have better fuzztesting now (hopefully)