The parser in accepts requests with a space (SP) right after the header name before the colon. This can lead to HTTP Request Smuggling (HRS) in llhttp < v2.1.4 and < v6.0.6.
{
"versions": [
{
"introduced": "0"
},
{
"last_affected": "20.3.4"
},
{
"introduced": "0"
},
{
"last_affected": "21.3.0"
}
]
}