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Category:   Application (Generic)  >   Red Hat Enterprise Virtualization Vendors:   Red Hat
(Red Hat Issues Fix for RHEV) GNU bash Environment Variable Processing Flaws Let Users Execute Arbitrary Code
SecurityTracker Alert ID:  1030963
SecurityTracker URL:  http://securitytracker.com/id/1030963
CVE Reference:   CVE-2014-6271, CVE-2014-7169, CVE-2014-7186, CVE-2014-7187   (Links to External Site)
Date:  Oct 2 2014
Impact:   Execution of arbitrary code via local system, Execution of arbitrary code via network, User access via local system, User access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  
Version(s): 3.4
Description:   Several vulnerabilities were reported in GNU bash. A user can execute arbitrary code on the target system. Red Hat Enterprise Virtualization is affected.

The software does not properly process environment variables.

A user can supply a specially crafted value that includes a bash function followed by additional code that, when processed by bash, will execute the additional code [CVE-2014-6271]. This vulnerability is known as "Shellshock".

Stephane Chazelas reported this vulnerability.

An initial fix for CVE-2014-6271 did not properly fix this flaw [CVE-2014-7169].

A user can supply a specially crafted value to trigger an out-of-bounds memory access in redir_stack() and potentially execute arbitrary code [CVE-2014-7186].

Florian Weimer of Red Hat Product Security reported this vulnerability.

A user can supply specially crafted, deeply nested flow control constructs to trigger an off-by-one error and potentially execute arbitrary code [CVE-2014-7187].

Florian Weimer of Red Hat Product Security reported this vulnerability.

A user can supply specially crafted data to access uninitialized memory and overwrite a pointer to potentially execute arbitrary code [CVE-2014-6277].

A user can supply specially crafted data to execute arbitrary code [CVE-2014-6278].

Michal Zalewski reported these vulnerabilities.

On a system with an application that passes data from a remote or remote authenticated user to bash, a remote or remote authenticated user may be able to exploit these vulnerabilities to execute arbitrary code.

Some common system application configurations are affected.

Demonstration exploit code is available.

This vulnerability is being actively exploited.

Impact:   A user can execute arbitrary code on the target system. In some application configurations, a remote user may be able to exploit this.
Solution:   Red Hat has issued a fix for CVE-2014-6271, CVE-2014-7169, CVE-2014-7186, and CVE-2014-7187 for Red Hat Enterprise Virtualization.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2014-1354.html

Vendor URL:  www.gnu.org/software/bash/ (Links to External Site)
Cause:   Input validation error
Underlying OS:  Linux (Red Hat Enterprise)

Message History:   This archive entry is a follow-up to the message listed below.
Sep 24 2014 GNU bash Environment Variable Processing Flaws Let Users Execute Arbitrary Code



 Source Message Contents

Subject:  [RHSA-2014:1354-01] Critical: rhev-hypervisor6 security update

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

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

Synopsis:          Critical: rhev-hypervisor6 security update
Advisory ID:       RHSA-2014:1354-01
Product:           Red Hat Enterprise Virtualization
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2014-1354.html
Issue date:        2014-10-02
CVE Names:         CVE-2014-1568 CVE-2014-6271 CVE-2014-7169 
                   CVE-2014-7186 CVE-2014-7187 
=====================================================================

1. Summary:

An updated rhev-hypervisor6 package that fixes several security issues is
now available.

Red Hat Product Security has rated this update as having Critical 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:

RHEV-M 3.4 - noarch

3. Description:

The rhev-hypervisor6 package provides a Red Hat Enterprise Virtualization
Hypervisor ISO disk image. The Red Hat Enterprise Virtualization Hypervisor
is a dedicated Kernel-based Virtual Machine (KVM) hypervisor. It includes
everything necessary to run and manage virtual machines: a subset of the
Red Hat Enterprise Linux operating environment and the Red Hat Enterprise
Virtualization Agent.

Note: Red Hat Enterprise Virtualization Hypervisor is only available for
the Intel 64 and AMD64 architectures with virtualization extensions.

A flaw was found in the way Bash evaluated certain specially crafted
environment variables. An attacker could use this flaw to override or
bypass environment restrictions to execute shell commands. Certain services
and applications allow remote unauthenticated attackers to provide
environment variables, allowing them to exploit this issue. (CVE-2014-6271)

It was found that the fix for CVE-2014-6271 was incomplete, and Bash still
allowed certain characters to be injected into other environments via
specially crafted environment variables. An attacker could potentially use
this flaw to override or bypass environment restrictions to execute shell
commands. Certain services and applications allow remote unauthenticated
attackers to provide environment variables, allowing them to exploit this
issue. (CVE-2014-7169)

A flaw was found in the way NSS parsed ASN.1 (Abstract Syntax Notation One)
input from certain RSA signatures. A remote attacker could use this flaw to
forge RSA certificates by providing a specially crafted signature to an
application using NSS. (CVE-2014-1568)

It was discovered that the fixed-sized redir_stack could be forced to
overflow in the Bash parser, resulting in memory corruption, and possibly
leading to arbitrary code execution when evaluating untrusted input that
would not otherwise be run as code. (CVE-2014-7186)

An off-by-one error was discovered in the way Bash was handling deeply
nested flow control constructs. Depending on the layout of the .bss
segment, this could allow arbitrary execution of code that would not
otherwise be executed by Bash. (CVE-2014-7187)

Red Hat would like to thank Stephane Chazelas for reporting CVE-2014-6271,
and the Mozilla project for reporting CVE-2014-1568. Upstream acknowledges
Antoine Delignat-Lavaud and Intel Product Security Incident Response Team
as the original reporters of CVE-2014-1568. The CVE-2014-7186 and
CVE-2014-7187 issues were discovered by Florian Weimer of Red Hat Product
Security.

Users of the Red Hat Enterprise Virtualization Hypervisor are advised to
upgrade to this updated package.

4. Solution:

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

To upgrade Hypervisors in Red Hat Enterprise Virtualization environments
using the disk image provided by this package, refer to:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/ht
ml/Hypervisor_Deployment_Guide/chap-Deployment_Guide-Upgrading_Red_Hat_Ente
rprise_Virtualization_Hypervisors.html

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

1141597 - CVE-2014-6271 bash: specially-crafted environment variables can be used to inject shell commands
1145429 - CVE-2014-1568 nss: RSA PKCS#1 signature verification forgery flaw (MFSA 2014-73)
1146319 - CVE-2014-7169 bash: code execution via specially-crafted environment (Incomplete fix for CVE-2014-6271)
1146791 - CVE-2014-7186 bash: parser can allow out-of-bounds memory access while handling redir_stack
1146804 - CVE-2014-7187 bash: off-by-one error in deeply nested flow control constructs

6. Package List:

RHEV-M 3.4:

Source:
rhev-hypervisor6-6.5-20140930.1.el6ev.src.rpm

noarch:
rhev-hypervisor6-6.5-20140930.1.el6ev.noarch.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-2014-1568.html
https://www.redhat.com/security/data/cve/CVE-2014-6271.html
https://www.redhat.com/security/data/cve/CVE-2014-7169.html
https://www.redhat.com/security/data/cve/CVE-2014-7186.html
https://www.redhat.com/security/data/cve/CVE-2014-7187.html
https://access.redhat.com/security/updates/classification/#critical

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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