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Category:   Application (Security)  >   Kerberos Vendors:   MIT
(Red Hat Issues Fix) Kerberos FTP Server Lets Remote Authenticated Users Read and Write Files With Elevated Privileges
SecurityTracker Alert ID:  1026713
SecurityTracker URL:  http://securitytracker.com/id/1026713
CVE Reference:   CVE-2011-1526   (Links to External Site)
Date:  Feb 21 2012
Impact:   Disclosure of system information, Disclosure of user information, Modification of user information
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  
Version(s): krb5-appl-1.0.1 and prior versions
Description:   A vulnerability was reported in Kerberos in the FTP daemon. A remote authenticated user can read and write files on the target system with elevated privileges.

A remote authenticated user can read and write files on the target system with the privileges of the group ID that started the FTP daemon. This is often root or wheel group privileges.

Tim Zingelman reported this vulnerability.

Impact:   A remote authenticated user can read and write files on the target system with the privileges of the group ID that started the FTP daemon.
Solution:   Red Hat has issued a fix.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2012-0306.html

Vendor URL:  web.mit.edu/kerberos/advisories/MITKRB5-SA-2011-005.txt (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.
Jul 5 2011 Kerberos FTP Server Lets Remote Authenticated Users Read and Write Files With Elevated Privileges



 Source Message Contents

Subject:  [RHSA-2012:0306-03] Low: krb5 security and bug fix update

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

Synopsis:          Low: krb5 security and bug fix update
Advisory ID:       RHSA-2012:0306-03
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2012-0306.html
Issue date:        2012-02-21
CVE Names:         CVE-2011-1526 
=====================================================================

1. Summary:

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

The Red Hat Security Response Team has rated this update as having low
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.

2. Relevant releases/architectures:

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

3. Description:

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).

It was found that ftpd, a Kerberos-aware FTP server, did not properly drop
privileges. On Red Hat Enterprise Linux 5, the ftpd daemon did not check
for the potential failure of the effective group ID change system call. If
the group ID change failed, a remote FTP user could use this flaw to gain
unauthorized read or write access to files that are owned by the root
group. (CVE-2011-1526)

Red Hat would like to thank the MIT Kerberos project for reporting this
issue. Upstream acknowledges Tim Zingelman as the original reporter.

This update also fixes the following bugs:

* Due to a mistake in the Kerberos libraries, a client could fail to
contact a Key Distribution Center (KDC) or terminate unexpectedly if the
client had already more than 1024 file descriptors in use. This update
backports modifications to the Kerberos libraries and the libraries use
the poll() function instead of the select() function, as poll() does not
have this limitation. (BZ#701444)

* The KDC failed to release memory when processing a TGS (ticket-granting
server) request from a client if the client request included an
authenticator with a subkey. As a result, the KDC consumed an excessive
amount of memory. With this update, the code releasing the memory has been
added and the problem no longer occurs. (BZ#708516)

* Under certain circumstances, if services requiring Kerberos
authentication sent two authentication requests to the authenticating
server, the second authentication request was flagged as a replay attack.
As a result, the second authentication attempt was denied. This update
applies an upstream patch that fixes this bug. (BZ#713500)

* Previously, if Kerberos credentials had expired, the klist command could
terminate unexpectedly with a segmentation fault when invoked with the -s
option. This happened when klist encountered and failed to process an entry
with no realm name while scanning the credential cache. With this update,
the underlying code has been modified and the command handles such entries
correctly. (BZ#729067)

* Due to a regression, multi-line FTP macros terminated prematurely with a
segmentation fault. This occurred because the previously-added patch failed
to properly support multi-line macros. This update restores the support for
multi-line macros and the problem no longer occurs. (BZ#735363, BZ#736132)

All users of krb5 are advised to upgrade to these updated packages, which
resolve these issues.

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/kb/docs/DOC-11259

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

701444 - Fix libkrb5 to work when > 1024 file descriptors are in use
708516 - memory leak during kdc TGS request
711419 - CVE-2011-1526 krb5, krb5-appl: ftpd incorrect group privilege dropping (MITKRB5-SA-2011-005)
729067 - klist -s segfaults with expired credentials
750823 - Newly introduced defect into krb5

6. Package List:

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

Source:
ftp://ftp.redhat.com/pub/redhat/linux/enterprise/5Client/en/os/SRPMS/krb5-1.6.1-70.el5.src.rpm

i386:
krb5-debuginfo-1.6.1-70.el5.i386.rpm
krb5-libs-1.6.1-70.el5.i386.rpm
krb5-workstation-1.6.1-70.el5.i386.rpm

x86_64:
krb5-debuginfo-1.6.1-70.el5.i386.rpm
krb5-debuginfo-1.6.1-70.el5.x86_64.rpm
krb5-libs-1.6.1-70.el5.i386.rpm
krb5-libs-1.6.1-70.el5.x86_64.rpm
krb5-workstation-1.6.1-70.el5.x86_64.rpm

RHEL Desktop Workstation (v. 5 client):

Source:
ftp://ftp.redhat.com/pub/redhat/linux/enterprise/5Client/en/os/SRPMS/krb5-1.6.1-70.el5.src.rpm

i386:
krb5-debuginfo-1.6.1-70.el5.i386.rpm
krb5-devel-1.6.1-70.el5.i386.rpm
krb5-server-1.6.1-70.el5.i386.rpm
krb5-server-ldap-1.6.1-70.el5.i386.rpm

x86_64:
krb5-debuginfo-1.6.1-70.el5.i386.rpm
krb5-debuginfo-1.6.1-70.el5.x86_64.rpm
krb5-devel-1.6.1-70.el5.i386.rpm
krb5-devel-1.6.1-70.el5.x86_64.rpm
krb5-server-1.6.1-70.el5.x86_64.rpm
krb5-server-ldap-1.6.1-70.el5.x86_64.rpm

Red Hat Enterprise Linux (v. 5 server):

Source:
ftp://ftp.redhat.com/pub/redhat/linux/enterprise/5Server/en/os/SRPMS/krb5-1.6.1-70.el5.src.rpm

i386:
krb5-debuginfo-1.6.1-70.el5.i386.rpm
krb5-devel-1.6.1-70.el5.i386.rpm
krb5-libs-1.6.1-70.el5.i386.rpm
krb5-server-1.6.1-70.el5.i386.rpm
krb5-server-ldap-1.6.1-70.el5.i386.rpm
krb5-workstation-1.6.1-70.el5.i386.rpm

ia64:
krb5-debuginfo-1.6.1-70.el5.i386.rpm
krb5-debuginfo-1.6.1-70.el5.ia64.rpm
krb5-devel-1.6.1-70.el5.ia64.rpm
krb5-libs-1.6.1-70.el5.i386.rpm
krb5-libs-1.6.1-70.el5.ia64.rpm
krb5-server-1.6.1-70.el5.ia64.rpm
krb5-server-ldap-1.6.1-70.el5.ia64.rpm
krb5-workstation-1.6.1-70.el5.ia64.rpm

ppc:
krb5-debuginfo-1.6.1-70.el5.ppc.rpm
krb5-debuginfo-1.6.1-70.el5.ppc64.rpm
krb5-devel-1.6.1-70.el5.ppc.rpm
krb5-devel-1.6.1-70.el5.ppc64.rpm
krb5-libs-1.6.1-70.el5.ppc.rpm
krb5-libs-1.6.1-70.el5.ppc64.rpm
krb5-server-1.6.1-70.el5.ppc.rpm
krb5-server-ldap-1.6.1-70.el5.ppc.rpm
krb5-workstation-1.6.1-70.el5.ppc.rpm

s390x:
krb5-debuginfo-1.6.1-70.el5.s390.rpm
krb5-debuginfo-1.6.1-70.el5.s390x.rpm
krb5-devel-1.6.1-70.el5.s390.rpm
krb5-devel-1.6.1-70.el5.s390x.rpm
krb5-libs-1.6.1-70.el5.s390.rpm
krb5-libs-1.6.1-70.el5.s390x.rpm
krb5-server-1.6.1-70.el5.s390x.rpm
krb5-server-ldap-1.6.1-70.el5.s390x.rpm
krb5-workstation-1.6.1-70.el5.s390x.rpm

x86_64:
krb5-debuginfo-1.6.1-70.el5.i386.rpm
krb5-debuginfo-1.6.1-70.el5.x86_64.rpm
krb5-devel-1.6.1-70.el5.i386.rpm
krb5-devel-1.6.1-70.el5.x86_64.rpm
krb5-libs-1.6.1-70.el5.i386.rpm
krb5-libs-1.6.1-70.el5.x86_64.rpm
krb5-server-1.6.1-70.el5.x86_64.rpm
krb5-server-ldap-1.6.1-70.el5.x86_64.rpm
krb5-workstation-1.6.1-70.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-2011-1526.html
https://access.redhat.com/security/updates/classification/#low
http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2011-005.txt

8. Contact:

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

Copyright 2012 Red Hat, Inc.
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