CVE-2023-3326: Network authentication attack via pam_krb5

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-06-22 · updated 2026-06-17
Weakness: CWE-303

Description

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.

Affected products

FreeBSD: before 12.4; from 13.0 before 13.1; 12.4, 12.4-p1, 12.4-p2, 12.4-rc2-p1, 12.4-rc2-p2, 13.1 (+11) — fixed in 12.4, 13.1

How to fix

Upgrade to a fixed version: FreeBSD 12.4, 13.1. Check the vendor advisory for mitigations.

References

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