MIT Kerberos 5: Multiple vulnerabilities

Background

MIT Kerberos 5 is a suite of applications that implement the Kerberos network protocol. kadmind is the MIT Kerberos 5 administration daemon, KDC is the Key Distribution Center.

Description

• Two vulnerabilities were found in the Kerberos 4 support in KDC: A global variable is not set for some incoming message types, leading to a NULL pointer dereference or a double free() (CVE-2008-0062) and unused portions of a buffer are not properly cleared when generating an error message, which results in stack content being contained in a reply (CVE-2008-0063).
• Jeff Altman (Secure Endpoints) discovered a buffer overflow in the RPC library server code, used in the kadmin server, caused when too many file descriptors are opened (CVE-2008-0947).
• Venustech AD-LAB discovered multiple vulnerabilities in the GSSAPI library: usage of a freed variable in the gss_indicate_mechs() function (CVE-2007-5901) and a double free() vulnerability in the gss_krb5int_make_seal_token_v3() function (CVE-2007-5971).

Impact

The first two vulnerabilities can be exploited by a remote unauthenticated attacker to execute arbitrary code on the host running krb5kdc, compromise the Kerberos key database or cause a Denial of Service. These bugs can only be triggered when Kerberos 4 support is enabled.

The RPC related vulnerability can be exploited by a remote unauthenticated attacker to crash kadmind, and theoretically execute arbitrary code with root privileges or cause database corruption. This bug can only be triggered in configurations that allow large numbers of open file descriptors in a process.

The GSSAPI vulnerabilities could be exploited by a remote attacker to cause Denial of Service conditions or possibly execute arbitrary code.

Workaround

Kerberos 4 support can be disabled via disabling the “krb4” USE flag and recompiling the ebuild, or setting “v4_mode=none” in the [kdcdefaults] section of /etc/krb5/kdc.conf. This will only work around the KDC related vulnerabilities.

Resolution

All MIT Kerberos 5 users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=app-crypt/mit-krb5-1.6.3-r1"