RHEL 5 : krb5 (RHSA-2010:0343)

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Synopsis :

The remote Red Hat host is missing one or more security updates.

Description :

Updated krb5 packages that fix one security issue and one bug are now
available for Red Hat Enterprise Linux 5.

The Red Hat Security Response Team has rated this update as having
important security impact. A Common Vulnerability Scoring System
(CVSS) base score, which gives a detailed severity rating, is
available from the CVE link in the References section.

Kerberos is a network authentication system which allows clients and
servers to authenticate to each other using symmetric encryption and a
trusted third party, the Key Distribution Center (KDC).

A use-after-free flaw was discovered in the MIT Kerberos
administration daemon, kadmind. A remote, authenticated attacker could
use this flaw to crash the kadmind daemon. Administrative privileges
are not required to trigger this flaw, as any realm user can request
information about their own principal from kadmind. (CVE-2010-0629)

This update also fixes the following bug :

* when a Kerberos client seeks tickets for use with a service, it must
contact the Key Distribution Center (KDC) to obtain them. The client
must also determine which realm the service belongs to and it
typically does this with a combination of client configuration detail,
DNS information and guesswork.

If the service belongs to a realm other than the client's, cross-realm
authentication is required. Using a combination of client
configuration and guesswork, the client determines the trust
relationship sequence which forms the trusted path between the
client's realm and the service's realm. This may include one or more
intermediate realms.

Anticipating the KDC has better knowledge of extant trust
relationships, the client then requests a ticket from the service's
KDC, indicating it will accept guidance from the service's KDC by
setting a special flag in the request. A KDC which recognizes the flag
can, at its option, return a ticket-granting ticket for the next realm
along the trust path the client should be following.

If the ticket-granting ticket returned by the service's KDC is for use
with a realm the client has already determined was in the trusted
path, the client accepts this as an optimization and continues. If,
however, the ticket is for use in a realm the client is not expecting,
the client responds incorrectly: it treats the case as an error rather
than continuing along the path suggested by the service's KDC.

For this update, the krb5 1.7 modifications which allow the client to
trust such KDCs to send them along the correct path, resulting in the
client obtaining the tickets it originally desired, were backported to
krb 1.6.1 (the version shipped with Red Hat Enterprise Linux 5.5).
(BZ#578540)

All krb5 users should upgrade to these updated packages, which contain
backported patches to correct these issues. All running KDC services
must be restarted for the update to take effect.

See also :

https://www.redhat.com/security/data/cve/CVE-2010-0629.html
http://rhn.redhat.com/errata/RHSA-2010-0343.html

Solution :

Update the affected packages.

Risk factor :

Medium / CVSS Base Score : 4.0
(CVSS2#AV:N/AC:L/Au:S/C:N/I:N/A:P)

Family: Red Hat Local Security Checks

Nessus Plugin ID: 46296 ()

Bugtraq ID:

CVE ID: CVE-2010-0629