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Category:   Application (Generic)  >   GNU bash Vendors:   GNU [multiple authors]
(Red Hat Issues Fix) GNU bash Environment Variable Processing Flaw Lets Users Execute Arbitrary Code
SecurityTracker Alert ID:  1030891
SecurityTracker URL:  http://securitytracker.com/id/1030891
CVE Reference:   CVE-2014-6271   (Links to External Site)
Updated:  Sep 26 2014
Original Entry Date:  Sep 24 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-2014-6271.

The Red Hat advisories are available at:

https://rhn.redhat.com/errata/RHSA-2014-1293.html
https://rhn.redhat.com/errata/RHSA-2014-1294.html
https://rhn.redhat.com/errata/RHSA-2014-1295.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:  4, 5, 5.6, 5.9, 6, 6.2, 6.4, 7

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-2014:1293-01] Critical: bash security update

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

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

Synopsis:          Critical: bash security update
Advisory ID:       RHSA-2014:1293-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2014-1293.html
Issue date:        2014-09-24
CVE Names:         CVE-2014-6271 
=====================================================================

1. Summary:

Updated bash packages that fix one security issue are now available for Red
Hat Enterprise Linux 5, 6, and 7.

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

Red Hat Enterprise Linux (v. 5 server) - i386, ia64, ppc, s390x, x86_64
Red Hat Enterprise Linux Client (v. 7) - x86_64
Red Hat Enterprise Linux Client Optional (v. 7) - x86_64
Red Hat Enterprise Linux ComputeNode (v. 7) - x86_64
Red Hat Enterprise Linux ComputeNode Optional (v. 7) - x86_64
Red Hat Enterprise Linux Desktop (v. 5 client) - i386, x86_64
Red Hat Enterprise Linux Desktop (v. 6) - i386, x86_64
Red Hat Enterprise Linux Desktop Optional (v. 6) - i386, x86_64
Red Hat Enterprise Linux HPC Node (v. 6) - x86_64
Red Hat Enterprise Linux HPC Node Optional (v. 6) - x86_64
Red Hat Enterprise Linux Server (v. 6) - i386, ppc64, s390x, x86_64
Red Hat Enterprise Linux Server (v. 7) - ppc64, s390x, x86_64
Red Hat Enterprise Linux Server Optional (v. 6) - i386, ppc64, s390x, x86_64
Red Hat Enterprise Linux Server Optional (v. 7) - ppc64, s390x, x86_64
Red Hat Enterprise Linux Workstation (v. 6) - i386, x86_64
Red Hat Enterprise Linux Workstation (v. 7) - x86_64
Red Hat Enterprise Linux Workstation Optional (v. 6) - i386, x86_64
Red Hat Enterprise Linux Workstation Optional (v. 7) - 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.

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)

For additional information on the CVE-2014-6271 flaw, refer to the
Knowledgebase article at https://access.redhat.com/articles/1200223

Red Hat would like to thank Stephane Chazelas for reporting this issue.

All bash users 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/):

1141597 - CVE-2014-6271 bash: specially-crafted environment variables can be used to inject shell commands

6. Package List:

Red Hat Enterprise Linux Desktop (v. 5 client):

Source:
bash-3.2-33.el5.1.src.rpm

i386:
bash-3.2-33.el5.1.i386.rpm
bash-debuginfo-3.2-33.el5.1.i386.rpm

x86_64:
bash-3.2-33.el5.1.x86_64.rpm
bash-debuginfo-3.2-33.el5.1.x86_64.rpm

Red Hat Enterprise Linux (v. 5 server):

Source:
bash-3.2-33.el5.1.src.rpm

i386:
bash-3.2-33.el5.1.i386.rpm
bash-debuginfo-3.2-33.el5.1.i386.rpm

ia64:
bash-3.2-33.el5.1.i386.rpm
bash-3.2-33.el5.1.ia64.rpm
bash-debuginfo-3.2-33.el5.1.i386.rpm
bash-debuginfo-3.2-33.el5.1.ia64.rpm

ppc:
bash-3.2-33.el5.1.ppc.rpm
bash-debuginfo-3.2-33.el5.1.ppc.rpm

s390x:
bash-3.2-33.el5.1.s390x.rpm
bash-debuginfo-3.2-33.el5.1.s390x.rpm

x86_64:
bash-3.2-33.el5.1.x86_64.rpm
bash-debuginfo-3.2-33.el5.1.x86_64.rpm

Red Hat Enterprise Linux Desktop (v. 6):

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

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

x86_64:
bash-4.1.2-15.el6_5.1.x86_64.rpm
bash-debuginfo-4.1.2-15.el6_5.1.x86_64.rpm

Red Hat Enterprise Linux Desktop Optional (v. 6):

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

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

x86_64:
bash-debuginfo-4.1.2-15.el6_5.1.x86_64.rpm
bash-doc-4.1.2-15.el6_5.1.x86_64.rpm

Red Hat Enterprise Linux HPC Node (v. 6):

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

x86_64:
bash-4.1.2-15.el6_5.1.x86_64.rpm
bash-debuginfo-4.1.2-15.el6_5.1.x86_64.rpm

Red Hat Enterprise Linux HPC Node Optional (v. 6):

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

x86_64:
bash-debuginfo-4.1.2-15.el6_5.1.x86_64.rpm
bash-doc-4.1.2-15.el6_5.1.x86_64.rpm

Red Hat Enterprise Linux Server (v. 6):

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

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

ppc64:
bash-4.1.2-15.el6_5.1.ppc64.rpm
bash-debuginfo-4.1.2-15.el6_5.1.ppc64.rpm

s390x:
bash-4.1.2-15.el6_5.1.s390x.rpm
bash-debuginfo-4.1.2-15.el6_5.1.s390x.rpm

x86_64:
bash-4.1.2-15.el6_5.1.x86_64.rpm
bash-debuginfo-4.1.2-15.el6_5.1.x86_64.rpm

Red Hat Enterprise Linux Server Optional (v. 6):

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

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

ppc64:
bash-debuginfo-4.1.2-15.el6_5.1.ppc64.rpm
bash-doc-4.1.2-15.el6_5.1.ppc64.rpm

s390x:
bash-debuginfo-4.1.2-15.el6_5.1.s390x.rpm
bash-doc-4.1.2-15.el6_5.1.s390x.rpm

x86_64:
bash-debuginfo-4.1.2-15.el6_5.1.x86_64.rpm
bash-doc-4.1.2-15.el6_5.1.x86_64.rpm

Red Hat Enterprise Linux Workstation (v. 6):

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

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

x86_64:
bash-4.1.2-15.el6_5.1.x86_64.rpm
bash-debuginfo-4.1.2-15.el6_5.1.x86_64.rpm

Red Hat Enterprise Linux Workstation Optional (v. 6):

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

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

x86_64:
bash-debuginfo-4.1.2-15.el6_5.1.x86_64.rpm
bash-doc-4.1.2-15.el6_5.1.x86_64.rpm

Red Hat Enterprise Linux Client (v. 7):

Source:
bash-4.2.45-5.el7_0.2.src.rpm

x86_64:
bash-4.2.45-5.el7_0.2.x86_64.rpm
bash-debuginfo-4.2.45-5.el7_0.2.x86_64.rpm

Red Hat Enterprise Linux Client Optional (v. 7):

x86_64:
bash-debuginfo-4.2.45-5.el7_0.2.x86_64.rpm
bash-doc-4.2.45-5.el7_0.2.x86_64.rpm

Red Hat Enterprise Linux ComputeNode (v. 7):

Source:
bash-4.2.45-5.el7_0.2.src.rpm

x86_64:
bash-4.2.45-5.el7_0.2.x86_64.rpm
bash-debuginfo-4.2.45-5.el7_0.2.x86_64.rpm

Red Hat Enterprise Linux ComputeNode Optional (v. 7):

x86_64:
bash-debuginfo-4.2.45-5.el7_0.2.x86_64.rpm
bash-doc-4.2.45-5.el7_0.2.x86_64.rpm

Red Hat Enterprise Linux Server (v. 7):

Source:
bash-4.2.45-5.el7_0.2.src.rpm

ppc64:
bash-4.2.45-5.el7_0.2.ppc64.rpm
bash-debuginfo-4.2.45-5.el7_0.2.ppc64.rpm

s390x:
bash-4.2.45-5.el7_0.2.s390x.rpm
bash-debuginfo-4.2.45-5.el7_0.2.s390x.rpm

x86_64:
bash-4.2.45-5.el7_0.2.x86_64.rpm
bash-debuginfo-4.2.45-5.el7_0.2.x86_64.rpm

Red Hat Enterprise Linux Server Optional (v. 7):

ppc64:
bash-debuginfo-4.2.45-5.el7_0.2.ppc64.rpm
bash-doc-4.2.45-5.el7_0.2.ppc64.rpm

s390x:
bash-debuginfo-4.2.45-5.el7_0.2.s390x.rpm
bash-doc-4.2.45-5.el7_0.2.s390x.rpm

x86_64:
bash-debuginfo-4.2.45-5.el7_0.2.x86_64.rpm
bash-doc-4.2.45-5.el7_0.2.x86_64.rpm

Red Hat Enterprise Linux Workstation (v. 7):

Source:
bash-4.2.45-5.el7_0.2.src.rpm

x86_64:
bash-4.2.45-5.el7_0.2.x86_64.rpm
bash-debuginfo-4.2.45-5.el7_0.2.x86_64.rpm

Red Hat Enterprise Linux Workstation Optional (v. 7):

x86_64:
bash-debuginfo-4.2.45-5.el7_0.2.x86_64.rpm
bash-doc-4.2.45-5.el7_0.2.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-2014-6271.html
https://access.redhat.com/security/updates/classification/#critical
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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