YAML versions before 1.27_001 for Perl allow a loaded perl/glob document to replace any package variable, which can lead to arbitrary code execution.
A perl/glob document names a package and a symbol, and supplies the value assigned to it. Nothing restricts the name, so the target can be @INC or YAML's own load options.
A perl/glob document that sets $YAML::LoadCode or $YAML::UseCode turns on code loading, which is off by default, for every later Load() in the process. A perl/code document is then passed to a string eval, so an attacker who supplies two documents to separate Load() calls in one process can execute arbitrary Perl code.
{
"extracted_events": [
{
"range": [
{
"introduced": "0"
},
{
"fixed": "1.27_001"
}
],
"source": "DESCRIPTION"
},
{
"range": [
{
"fixed": "bace96b5e6661d521c7c515c94a09e081c911fce"
}
],
"source": "REFERENCES_COMMIT"
}
]
}