The client side in OpenSSH 5.7 through 8.4 has an Observable Discrepancy leading to an information leak in the algorithm negotiation. This allows man-in-the-middle attackers to target initial connection attempts (where no host key for the server has been cached by the client). NOTE: some reports state that 8.5 and 8.6 are also affected.
{
"versions": [
{
"introduced": "5.7"
},
{
"fixed": "8.4"
},
{
"introduced": "0"
},
{
"last_affected": "8.4-NA"
},
{
"introduced": "0"
},
{
"last_affected": "8.5-NA"
},
{
"introduced": "0"
},
{
"last_affected": "8.6-NA"
}
]
}