Bug 208430

Summary:	CVE-2006-5051 unsafe GSSAPI signal handler
Product:	Red Hat Enterprise Linux 2.1	Reporter:	Josh Bressers <bressers>
Component:	openssh	Assignee:	Tomas Mraz <tmraz>
Status:	CLOSED ERRATA	QA Contact:	Brian Brock <bbrock>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	2.1	Keywords:	Security
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:	reported=20060928,source=vendorsec,impact=important,public=20060928
Fixed In Version:	RHSA-2006-0698	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2006-09-29 00:25:03 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Josh Bressers 2006-09-28 15:21:22 UTC

+++ This bug was initially created as a clone of Bug #208347 +++

OpenSSH 4.4 was released and mentions:

        * Fix an unsafe signal hander reported by Mark Dowd. The
        signal handler was vulnerable to a race condition that could
        be exploited to perform a pre-authentication denial of
        service. On portable OpenSSH, this vulnerability could
        theoretically lead to pre-authentication remote code execution
        if GSSAPI authentication is enabled, but the likelihood of
        successful exploitation appears remote.


-- Additional comment from bressers on 2006-09-28 11:17 EST --
I've done some analysis of this issue and received a mail from Mark Dowd
regarding this vulnerability.  The upstream details are misleading.

The problem is that the signal handling in openssh does quite a lot and can
introduce a race condition during cleanup.  This flaw could possibly cause a
double free condition within the kerberos cleanup code.  The GSSAPI code is
completely harmless, upstream calling this issue a GSSAPI issue leads me to
believe they did not analyze, nor try to understand, this issue.

There is also PAM cleanup code which is executed.  This PAM source hasn't been
investigated so the possible outcome is currently unknown.

Red Hat will be fixing this issue due to the incredible complexity and possible
danger.  This is a case of better safe than sorry.

Comment 2 Red Hat Bugzilla 2006-09-29 00:25:04 UTC

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.

http://rhn.redhat.com/errata/RHSA-2006-0698.html