pam_krb5 authenticates a user by essentially running kinit with the password, getting a ticket-granting ticket (tgt) from the Kerberos KDC (Key Distribution Center) over the network, as a way to verify the password. However, if a keytab is not provisioned on the system, pam_krb5 has no way to validate the response from the KDC, and essentially trusts the tgt provided over the network as being valid. In a non-default FreeBSD installation that leverages pam_krb5 for authentication and does not have a keytab provisioned, an attacker that is able to control both the password and the KDC responses can return a valid tgt, allowing authentication to occur for any user on the system.
[
{
"defaultStatus": "unaffected",
"modules": [
"pam_krb5"
],
"product": "FreeBSD",
"vendor": "FreeBSD",
"versions": [
{
"lessThan": "13.2-RELEASE-p1",
"status": "affected",
"version": "13.2-RELEASE",
"versionType": "release"
},
{
"lessThan": "13.1-RELEASE-p8",
"status": "affected",
"version": "13.1-RELEASE",
"versionType": "release"
},
{
"lessThan": "12.4-RELEASE-p3",
"status": "affected",
"version": "12.4-RELEASE",
"versionType": "release"
}
]
}
]