RHSA-2005:562 - Security Advisory

Topic

Updated krb5 packages which fix multiple security issues are now available
for Red Hat Enterprise Linux 2.1 and 3.

This update has been rated as having critical security impact by the Red
Hat Security Response Team.

[Updated 26 Sep 2005]
krb5-server packages have been added to this advisory for Red Hat
Enterprise Linux 3 WS and Red Hat Enterprise Linux 3 Desktop.

Description

Kerberos is a networked authentication system which uses a trusted third
party (a KDC) to authenticate clients and servers to each other.

A double-free flaw was found in the krb5_recvauth() routine which may be
triggered by a remote unauthenticated attacker. Although no exploit is
currently known to exist, this issue could potentially be exploited to
allow arbitrary code execution on a Key Distribution Center (KDC). The
Common Vulnerabilities and Exposures project assigned the name
CAN-2005-1689 to this issue.

Daniel Wachdorf discovered a single byte heap overflow in the
krb5_unparse_name() function, part of krb5-libs. Sucessful exploitation of
this flaw would lead to a denial of service (crash). To trigger this flaw
an attacker would need to have control of a kerberos realm that shares a
cross-realm key with the target, making exploitation of this flaw unlikely.
(CAN-2005-1175).

Gaël Delalleau discovered an information disclosure issue in the way
some telnet clients handle messages from a server. An attacker could
construct a malicious telnet server that collects information from the
environment of any victim who connects to it using the Kerberos-aware
telnet client (CAN-2005-0488).

The rcp protocol allows a server to instruct a client to write to arbitrary
files outside of the current directory. This could potentially cause a
security issue if a user uses the Kerberos-aware rcp to copy files from a
malicious server (CAN-2004-0175).

All users of krb5 should update to these erratum packages which contain
backported patches to correct these issues. Red Hat would like to thank
the MIT Kerberos Development Team for their responsible disclosure of these
issues.

Solution

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

This update is available via Red Hat Network. To use Red Hat Network,
launch the Red Hat Update Agent with the following command:

up2date

This will start an interactive process that will result in the appropriate
RPMs being upgraded on your system.

Affected Products

• Red Hat Enterprise Linux Server 3 x86_64
• Red Hat Enterprise Linux Server 3 ia64
• Red Hat Enterprise Linux Server 3 i386
• Red Hat Enterprise Linux Server 2 ia64
• Red Hat Enterprise Linux Server 2 i386
• Red Hat Enterprise Linux Workstation 3 x86_64
• Red Hat Enterprise Linux Workstation 3 ia64
• Red Hat Enterprise Linux Workstation 3 i386
• Red Hat Enterprise Linux Workstation 2 ia64
• Red Hat Enterprise Linux Workstation 2 i386
• Red Hat Enterprise Linux Desktop 3 x86_64
• Red Hat Enterprise Linux Desktop 3 i386
• Red Hat Enterprise Linux for IBM z Systems 3 s390x
• Red Hat Enterprise Linux for IBM z Systems 3 s390
• Red Hat Enterprise Linux for Power, big endian 3 ppc

Fixes

• BZ - 159304 - CAN-2005-0488 telnet Information Disclosure Vulnerability
• BZ - 159753 - CAN-2005-1689 double-free in krb5_recvauth
• BZ - 161471 - krb5 krb5_principal_compare NULL pointer crash
• BZ - 161611 - CAN-2004-0175 malicious rsh server can cause rcp to write to arbitrary files
• BZ - 162255 - CAN-2005-1175 krb5 buffer overflow in KDC

CVEs

• CVE-2005-0488
• CVE-2005-1689
• CVE-2005-1175
• CVE-2004-0175

References

• http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2005-003-recvauth.txt
• http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2005-002-kdc.txt