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Category:   Application (Security)  >   Kerberos Vendors:   MIT
(Red Hat Issues Fix) Kerberos KDC Null Pointer Dereference for Multi-Realm KDCs Lets Remote Users Deny Service
SecurityTracker Alert ID:  1030857
SecurityTracker URL:  http://securitytracker.com/id/1030857
CVE Reference:   CVE-2013-1418   (Links to External Site)
Date:  Sep 17 2014
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  

Description:   A vulnerability was reported in Kerberos. A remote user can cause denial of service conditions.

A remote user can send specially crafted requests to trigger a null pointer dereference and cause the target KDC to crash.

KDCs configured to serve multiple realms are affected.

The vulnerability resides in the setup_server_realm() function in 'src/kdc/main.c'.

Impact:   A remote user can cause the target KDC to crash.
Solution:   Red Hat has issued a fix.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2014-1245.html

Vendor URL:  web.mit.edu/kerberos/ (Links to External Site)
Cause:   Access control error
Underlying OS:  Linux (Red Hat Enterprise)
Underlying OS Comments:  5

Message History:   This archive entry is a follow-up to the message listed below.
Nov 6 2013 Kerberos KDC Null Pointer Dereference for Multi-Realm KDCs Lets Remote Users Deny Service



 Source Message Contents

Subject:  [RHSA-2014:1245-01] Moderate: krb5 security and bug fix update

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=====================================================================
                   Red Hat Security Advisory

Synopsis:          Moderate: krb5 security and bug fix update
Advisory ID:       RHSA-2014:1245-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2014-1245.html
Issue date:        2014-09-16
CVE Names:         CVE-2013-1418 CVE-2013-6800 CVE-2014-4341 
                   CVE-2014-4344 
=====================================================================

1. Summary:

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.

2. Relevant releases/architectures:

Red Hat Enterprise Linux (v. 5 server) - i386, ia64, ppc, s390x, x86_64
Red Hat Enterprise Linux Desktop (v. 5 client) - i386, x86_64
Red Hat Enterprise Linux Desktop Workstation (v. 5 client) - i386, x86_64

3. 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.

4. 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

5. Bugs fixed (https://bugzilla.redhat.com/):

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

6. Package List:

Red Hat Enterprise Linux Desktop (v. 5 client):

Source:
krb5-1.6.1-78.el5.src.rpm

i386:
krb5-debuginfo-1.6.1-78.el5.i386.rpm
krb5-libs-1.6.1-78.el5.i386.rpm
krb5-workstation-1.6.1-78.el5.i386.rpm

x86_64:
krb5-debuginfo-1.6.1-78.el5.i386.rpm
krb5-debuginfo-1.6.1-78.el5.x86_64.rpm
krb5-libs-1.6.1-78.el5.i386.rpm
krb5-libs-1.6.1-78.el5.x86_64.rpm
krb5-workstation-1.6.1-78.el5.x86_64.rpm

Red Hat Enterprise Linux Desktop Workstation (v. 5 client):

Source:
krb5-1.6.1-78.el5.src.rpm

i386:
krb5-debuginfo-1.6.1-78.el5.i386.rpm
krb5-devel-1.6.1-78.el5.i386.rpm
krb5-server-1.6.1-78.el5.i386.rpm
krb5-server-ldap-1.6.1-78.el5.i386.rpm

x86_64:
krb5-debuginfo-1.6.1-78.el5.i386.rpm
krb5-debuginfo-1.6.1-78.el5.x86_64.rpm
krb5-devel-1.6.1-78.el5.i386.rpm
krb5-devel-1.6.1-78.el5.x86_64.rpm
krb5-server-1.6.1-78.el5.x86_64.rpm
krb5-server-ldap-1.6.1-78.el5.x86_64.rpm

Red Hat Enterprise Linux (v. 5 server):

Source:
krb5-1.6.1-78.el5.src.rpm

i386:
krb5-debuginfo-1.6.1-78.el5.i386.rpm
krb5-devel-1.6.1-78.el5.i386.rpm
krb5-libs-1.6.1-78.el5.i386.rpm
krb5-server-1.6.1-78.el5.i386.rpm
krb5-server-ldap-1.6.1-78.el5.i386.rpm
krb5-workstation-1.6.1-78.el5.i386.rpm

ia64:
krb5-debuginfo-1.6.1-78.el5.i386.rpm
krb5-debuginfo-1.6.1-78.el5.ia64.rpm
krb5-devel-1.6.1-78.el5.ia64.rpm
krb5-libs-1.6.1-78.el5.i386.rpm
krb5-libs-1.6.1-78.el5.ia64.rpm
krb5-server-1.6.1-78.el5.ia64.rpm
krb5-server-ldap-1.6.1-78.el5.ia64.rpm
krb5-workstation-1.6.1-78.el5.ia64.rpm

ppc:
krb5-debuginfo-1.6.1-78.el5.ppc.rpm
krb5-debuginfo-1.6.1-78.el5.ppc64.rpm
krb5-devel-1.6.1-78.el5.ppc.rpm
krb5-devel-1.6.1-78.el5.ppc64.rpm
krb5-libs-1.6.1-78.el5.ppc.rpm
krb5-libs-1.6.1-78.el5.ppc64.rpm
krb5-server-1.6.1-78.el5.ppc.rpm
krb5-server-ldap-1.6.1-78.el5.ppc.rpm
krb5-workstation-1.6.1-78.el5.ppc.rpm

s390x:
krb5-debuginfo-1.6.1-78.el5.s390.rpm
krb5-debuginfo-1.6.1-78.el5.s390x.rpm
krb5-devel-1.6.1-78.el5.s390.rpm
krb5-devel-1.6.1-78.el5.s390x.rpm
krb5-libs-1.6.1-78.el5.s390.rpm
krb5-libs-1.6.1-78.el5.s390x.rpm
krb5-server-1.6.1-78.el5.s390x.rpm
krb5-server-ldap-1.6.1-78.el5.s390x.rpm
krb5-workstation-1.6.1-78.el5.s390x.rpm

x86_64:
krb5-debuginfo-1.6.1-78.el5.i386.rpm
krb5-debuginfo-1.6.1-78.el5.x86_64.rpm
krb5-devel-1.6.1-78.el5.i386.rpm
krb5-devel-1.6.1-78.el5.x86_64.rpm
krb5-libs-1.6.1-78.el5.i386.rpm
krb5-libs-1.6.1-78.el5.x86_64.rpm
krb5-server-1.6.1-78.el5.x86_64.rpm
krb5-server-ldap-1.6.1-78.el5.x86_64.rpm
krb5-workstation-1.6.1-78.el5.x86_64.rpm

These packages are GPG signed by Red Hat for security.  Our key and
details on how to verify the signature are available from
https://access.redhat.com/security/team/key/#package

7. References:

https://www.redhat.com/security/data/cve/CVE-2013-1418.html
https://www.redhat.com/security/data/cve/CVE-2013-6800.html
https://www.redhat.com/security/data/cve/CVE-2014-4341.html
https://www.redhat.com/security/data/cve/CVE-2014-4344.html
https://access.redhat.com/security/updates/classification/#moderate

8. Contact:

The Red Hat security contact is <secalert@redhat.com>.  More contact
details at https://access.redhat.com/security/team/contact/

Copyright 2014 Red Hat, Inc.
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