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Category:   Application (Generic)  >   GNU bash Vendors:   GNU [multiple authors]
(Red Hat Issues Fix) GNU bash Environment Variable Processing Flaws Let Users Execute Arbitrary Code
SecurityTracker Alert ID:  1030928
SecurityTracker URL:  http://securitytracker.com/id/1030928
CVE Reference:   CVE-2014-7169, CVE-2014-7186, CVE-2014-7187   (Links to External Site)
Date:  Sep 26 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): 4.3
Description:   Several vulnerabilities were reported in GNU bash. A user can execute arbitrary code on the target system.

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-2014-7169, CVE-2014-7186, and CVE-2014-7187.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2014-1312.html

Vendor URL:  www.gnu.org/software/bash/ (Links to External Site)
Cause:   Input validation error
Underlying OS:  Linux (Red Hat Enterprise)
Underlying OS Comments:  5, 6

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-2014:1312-01] Important: bash Shift_JIS security update

-----BEGIN PGP SIGNED MESSAGE-----
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=====================================================================
                   Red Hat Security Advisory

Synopsis:          Important: bash Shift_JIS security update
Advisory ID:       RHSA-2014:1312-01
Product:           RHEL S-JIS Service
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2014-1312.html
Issue date:        2014-09-26
CVE Names:         CVE-2014-7169 CVE-2014-7186 CVE-2014-7187 
=====================================================================

1. Summary:

Updated bash Shift_JIS packages that fix one security issue are now
available for Red Hat Enterprise Linux 5 and 6.

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

S-JIS for Red Hat Enteprise Linux 5 Server - i386, ia64, x86_64
S-JIS for Red Hat Enteprise Linux 6 Server - i386, x86_64

3. Description:

The GNU Bourne Again shell (Bash) is a shell and command language
interpreter compatible with the Bourne shell (sh). Bash is the default
shell for Red Hat Enterprise Linux.

Shift_JIS, also known as "SJIS", is a character encoding for the Japanese
language. This package provides bash support for the Shift_JIS encoding.

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)

Applications which directly create Bash functions as environment variables
need to be made aware of the changes to the way names are handled by this
update. For more information see the Knowledgebase article at
https://access.redhat.com/articles/1200223

Note: Docker users are advised to use "yum update" within their containers,
and to commit the resulting changes.

For additional information on CVE-2014-6271 and CVE-2014-7169, refer to the
aforementioned Knowledgebase article.

All users who require Shift_JIS encoding support with Bash built-in
functions are advised to upgrade to these updated packages, which contain a
backported patch to correct this issue.

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/articles/11258

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

1146319 - CVE-2014-7169 bash: code execution via specially-crafted environment (Incomplete fix for CVE-2014-6271)

6. Package List:

S-JIS for Red Hat Enteprise Linux 5 Server:

Source:
bash-3.2-33.el5_11.1.sjis.2.src.rpm

i386:
bash-3.2-33.el5_11.1.sjis.2.i386.rpm
bash-debuginfo-3.2-33.el5_11.1.sjis.2.i386.rpm

ia64:
bash-3.2-33.el5_11.1.sjis.2.i386.rpm
bash-3.2-33.el5_11.1.sjis.2.ia64.rpm
bash-debuginfo-3.2-33.el5_11.1.sjis.2.i386.rpm
bash-debuginfo-3.2-33.el5_11.1.sjis.2.ia64.rpm

x86_64:
bash-3.2-33.el5_11.1.sjis.2.x86_64.rpm
bash-debuginfo-3.2-33.el5_11.1.sjis.2.x86_64.rpm

S-JIS for Red Hat Enteprise Linux 6 Server:

Source:
bash-4.1.2-15.el6_5.1.sjis.2.src.rpm

i386:
bash-4.1.2-15.el6_5.1.sjis.2.i686.rpm
bash-debuginfo-4.1.2-15.el6_5.1.sjis.2.i686.rpm
bash-doc-4.1.2-15.el6_5.1.sjis.2.i686.rpm

x86_64:
bash-4.1.2-15.el6_5.1.sjis.2.x86_64.rpm
bash-debuginfo-4.1.2-15.el6_5.1.sjis.2.x86_64.rpm
bash-doc-4.1.2-15.el6_5.1.sjis.2.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-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/#important
https://access.redhat.com/articles/1200223

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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