Bug 229782 (CVE-2007-0956)

Summary: CVE-2007-0956 Unauthorized access via krb5-telnet daemon
Product: Red Hat Enterprise Linux 4 Reporter: Marcel Holtmann <holtmann>
Component: krb5Assignee: Nalin Dahyabhai <nalin>
Status: CLOSED ERRATA QA Contact: Brian Brock <bbrock>
Severity: urgent Docs Contact:
Priority: urgent    
Version: 4.0CC: jplans, nmiell, security-response-team
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard: impact=critical,source=mit,reported=20070221,public=20070403
Fixed In Version: RHSA-2007-0095 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2007-04-03 14:21:32 EDT Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Description Marcel Holtmann 2007-02-23 09:36:08 EST
The MIT krb5 telnet daemon (telnetd) allows unauthorized login as an arbitrary
user, when presented with a specially crafted username. This is a vulnerability
in an application program; it is not a bug in the MIT krb5 libraries or in the
Kerberos protocol.

A user can gain unauthorized access to any account (including root) on a host
running telnetd. Whether the attacker needs to authenticate depends on the
configuration of telnetd on that host.

The telnetd in all releases of MIT krb5, up to and including krb5-1.6 are affected.
Comment 1 Mark J. Cox 2007-02-23 09:59:46 EST
Note that by default we do not enable telnetd in RHEL and the firewall in RHEL
defaults to blocking external access to telnet.  

A server would be vulnerable to this flaw only if they enable krb5 telnetd using
"chkconfig krb5-telnet on" and set the firewall to allow incoming connections to
the telnet port.
Comment 4 Mark J. Cox 2007-03-06 03:52:44 EST
Embargo moved by MIT to 20070403
Comment 8 Mark J. Cox 2007-03-27 06:20:21 EDT
Note that this issue is similar to the telnetd flaw found in Solaris:
However the technicalities of the flaw are different, and exploitation is
different.  Therefore the exploits for the Solaris telnetd flaw, and the worm
that exploits the Solaris issue do not successfully exploit this issue.  

Whilst we are not aware of this issue currently being exploited we have
confirmed that an exploit is possible and is fairly easy to create.
Comment 10 Mark J. Cox 2007-04-03 14:08:30 EDT
Now public, removing embargo
Comment 11 Red Hat Bugzilla 2007-04-03 14:21:32 EDT
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

Comment 12 Lubomir Kundrak 2008-04-08 08:51:10 EDT
*** Bug 228233 has been marked as a duplicate of this bug. ***