In Jenkins 2.355 and earlier, LTS 2.332.3 and earlier, an observable timing discrepancy on the login form allows distinguishing between login attempts with an invalid username, and login attempts with a valid username and wrong password, when using the Jenkins user database security realm.
{
"versions": [
{
"introduced": "0"
},
{
"last_affected": "2.332.3"
},
{
"introduced": "0"
},
{
"last_affected": "2.355"
}
]
}