GeoServer through 2.18.5 and 2.19.x through 2.19.2 allows SSRF via the option for setting a proxy host.
{
"versions": [
{
"introduced": "0"
},
{
"last_affected": "2.18.5"
},
{
"introduced": "2.19.0"
},
{
"fixed": "2.19.3"
}
]
}