RHSA-2014:1245 - Security Advisory

Topic

Updated krb5 packages that fix multiple security issues and two bugs are
now available for Red Hat Enterprise Linux 5.

Red Hat Product Security has rated this update as having Moderate security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links in the References section.

Description

Kerberos is an authentication system which allows clients and services to
authenticate to each other with the help of a trusted third party, a
Kerberos Key Distribution Center (KDC).

It was found that if a KDC served multiple realms, certain requests could
cause the setup_server_realm() function to dereference a NULL pointer.
A remote, unauthenticated attacker could use this flaw to crash the KDC
using a specially crafted request. (CVE-2013-1418, CVE-2013-6800)

A NULL pointer dereference flaw was found in the MIT Kerberos SPNEGO
acceptor for continuation tokens. A remote, unauthenticated attacker could
use this flaw to crash a GSSAPI-enabled server application. (CVE-2014-4344)

A buffer over-read flaw was found in the way MIT Kerberos handled certain
requests. A man-in-the-middle attacker with a valid Kerberos ticket who is
able to inject packets into a client or server application's GSSAPI session
could use this flaw to crash the application. (CVE-2014-4341)

This update also fixes the following bugs:

• Prior to this update, the libkrb5 library occasionally attempted to free

already freed memory when encrypting credentials. As a consequence, the
calling process terminated unexpectedly with a segmentation fault.
With this update, libkrb5 frees memory correctly, which allows the
credentials to be encrypted appropriately and thus prevents the mentioned
crash. (BZ#1004632)

• Previously, when the krb5 client library was waiting for a response from

a server, the timeout variable in certain cases became a negative number.
Consequently, the client could enter a loop while checking for responses.
With this update, the client logic has been modified and the described
error no longer occurs. (BZ#1089732)

All krb5 users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. After installing the
updated packages, the krb5kdc daemon will be restarted automatically.

Solution

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to use the
Red Hat Network to apply this update are available at
https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 5 x86_64
• Red Hat Enterprise Linux Server 5 ia64
• Red Hat Enterprise Linux Server 5 i386
• Red Hat Enterprise Linux Workstation 5 x86_64
• Red Hat Enterprise Linux Workstation 5 i386
• Red Hat Enterprise Linux Desktop 5 x86_64
• Red Hat Enterprise Linux Desktop 5 i386
• Red Hat Enterprise Linux for IBM z Systems 5 s390x
• Red Hat Enterprise Linux for Power, big endian 5 ppc
• Red Hat Enterprise Linux Server from RHUI 5 x86_64
• Red Hat Enterprise Linux Server from RHUI 5 i386

Fixes

• BZ - 1026942 - CVE-2013-1418 krb5: multi-realm KDC null dereference leads to crash
• BZ - 1031499 - CVE-2013-6800 krb5: KDC remote DoS (NULL pointer dereference and daemon crash)
• BZ - 1116180 - CVE-2014-4341 krb5: denial of service flaws when handling padding length longer than the plaintext
• BZ - 1121877 - CVE-2014-4344 krb5: NULL pointer dereference flaw in SPNEGO acceptor for continuation tokens

CVEs

• CVE-2013-1418
• CVE-2014-4341
• CVE-2014-4344
• CVE-2013-6800

References

• https://access.redhat.com/security/updates/classification/#moderate