CVE-2023-3326
Published: 22 June 2023
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.
Notes
| Author | Note |
|---|---|
| mdeslaur | per the comments on the oss-sec post, "pam_krb5 and sssd-krb5 are both affected by the same attack, but they have always been _documented_ to be affected". See the "verify_ap_req_nofail" option in the man page. Deferring this CVE to see if a fix will be available, or if this isn't something that will ever get a fix because it works as documented. |
Mitigation
Per the documentation, set verify_ap_req_nofail to true in the [libdefaults] section of /etc/krb5.conf.
Priority
Status
| Package | Release | Status |
|---|---|---|
|
libpam-krb5 Launchpad, Ubuntu, Debian |
bionic |
Deferred
(2024-04-22)
|
| focal |
Deferred
(2024-04-22)
|
|
| jammy |
Deferred
(2024-04-22)
|
|
| kinetic |
Ignored
(end of life, was deferred [2024-04-22])
|
|
| lunar |
Ignored
(end of life, was deferred [2024-04-22])
|
|
| mantic |
Deferred
(2024-04-22)
|
|
| noble |
Deferred
(2024-04-22)
|
|
| trusty |
Deferred
(2024-04-22)
|
|
| upstream |
Needs triage
|
|
| xenial |
Deferred
(2024-04-22)
|
|
|
sssd Launchpad, Ubuntu, Debian |
bionic |
Deferred
(2024-04-22)
|
| focal |
Deferred
(2024-04-22)
|
|
| jammy |
Deferred
(2024-04-22)
|
|
| kinetic |
Ignored
(end of life, was deferred [2024-04-22])
|
|
| lunar |
Ignored
(end of life, was deferred [2024-04-22])
|
|
| mantic |
Deferred
(2024-04-22)
|
|
| noble |
Deferred
(2024-04-22)
|
|
| trusty |
Ignored
(end of standard support)
|
|
| upstream |
Needs triage
|
|
| xenial |
Deferred
(2024-04-22)
|
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score | 9.8 |
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity impact | High |
| Availability impact | High |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |