9.8 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8 High
AI Score
Confidence
High
10 High
CVSS2
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
AV:N/AC:L/Au:N/C:C/I:C/A:C
0.976 High
EPSS
Percentile
100.0%
This updated advisory is a follow-up to the original advisory titled ICSA-14-269-01 Bash Command Injection Vulnerability that was published September 26, 2014, on the NCCIC/ICS‑CERT web site.
A command injection vulnerability has been reported in the Bourne again shell (bash). Bash is the common command-line used in most Linux/Unix-based operating systems and Apple’s Mac OS X. The flaw could allow an attacker to remotely execute shell commands by attaching malicious code in environment variables used by the operating system.
Industrial control systems running embedded versions of Linux may not be field upgradeable are of particular concern and may require alternate mitigation.
Patches have been released to fix this vulnerability by major Linux vendors for affected versions. Solutions for CVE-2014-6271 do not completely resolve the vulnerability. It is advised to install existing patches and pay attention for updated patches to address CVE-2014-7169.
Exploits that target this vulnerability are publicly available.
As bash is a third-party component, asset owners, operators, and SCADA product developers are encouraged to investigate the use of the affected versions of bash in their environments. ICS-CERT encourages any asset owners/operators, developers, or vendors to coordinate known implementations of the affected products directly with ICS-CERT.
The following bash versions are affected:
Users may use Nessus to determine if their devices are running a vulnerable bash version:
ICS-CERT sent out a query to vendors we have collaborated with in the past. Many have responded back with information about which products are affected by this bash vulnerability. ICS-CERT created a supplement to this advisory that contains this information. It can be found at the following web location: https://ics-cert.us-cert.gov/advisories/Supplement-ICSA-14-269-01. This supplement will be updated with additional information as it becomes available, without updating this advisory.
An exploit using this vulnerability could allow an attacker to remotely execute arbitrary commands.
This vulnerability is classified by industry standards as “High” impact with CVSS Impact Subscore 10 and “Low” on complexity, which means it takes little skill to perform. This flaw allows attackers to provide specially crafted environment variables containing arbitrary commands that can be executed on vulnerable systems. It is especially dangerous because of the prevalent use of the bash shell and its ability to be called by an application in numerous ways.https://www.us-cert.gov/ncas/alerts/TA14-268A, web site last accessed September 26, 2014.
Impact to individual organizations depends on many factors that are unique to each organization. ICS-CERT recommends that organizations evaluate the impact of this vulnerability as based on their operational environment, architecture, and product implementation.
Bash is a command processor that allows users to type or input stored commands via a script. Originally written as a Unix shell by Brian Fox for the GNU project, it has become the default shell on Linux and Mac OS X. Various product adaptations have brought this shell to Microsoft (Cygwin and MinGW), DOS, Novell NetWare, and Android. Bash supports wildcards in file names, piping, variables, command substitution, and condition testing.
GNU bash through 4.3 processes trailing strings after function definitions in the values of environment variables, which allows remote attackers to execute arbitrary code via a crafted environment. OpenSSH, Apache HTTP Server, and DHCP clients could be particularly vulnerable.
CVE-2014-6271NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-6271, NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory. has been assigned to this vulnerability. A CVSS v2 base score of 10.0 has been assigned; the CVSS vector string is (AV:N/AC:L/Au:N/C:C/I:C/A:C).CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:L/Au:N/C:C/I:C/A:C, web site last accessed September 25, 2014.
This vulnerability could be exploited remotely.
Exploits that target this vulnerability are publicly available.
An attacker with a low skill would be able to exploit this vulnerability.
There are several functional mitigations for this vulnerability including upgrading to a new version of bash, replacing bash with an alternate shell, limiting access to vulnerable services, and/or filtering inputs to vulnerable services.
Patches have been released to fix this vulnerability by major Linux vendors for affected versions; however, solutions for CVE-2014-6271 do not completely resolve the vulnerability. It is advised to install existing patches and pay attention for updated patches to address CVE-2014-7169.Vulnerability Summary for CVE-2014-7169 http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-7169, web site last accessed September 26, 2014.
Many UNIX-like operating systems, including Linux distributions, BSD variants, and Apple Mac OS X include bash and are likely to be affected. Contact your respective Linux or Unix-based OS vendor(s) for updated information. A list of vendors can be found in CERT Vulnerability Note VU#252743.Vulnerability Note VU#252743, http://www.kb.cert.org/vuls/id/252743, web site last accessed September 26, 2014.
ICS-CERT recommends system administrators review the vendor patches and the NIST Vulnerability Summary for CVE-2014-7169e, to mitigate damage caused by the exploit
Other helpful resources include:
Support Information:
As bash may be used as a third-party component, asset owners, operators, and ICS software developers are encouraged to investigate the use of the affected versions of bash in their environments.
The ST and PT ISAC released the following test string to determine detect vulnerable installations.
To check if you are patched, you can use the original test string:
env x=‘() { :;}; echo vulnerable’ bash -c “echo this is a test”
If you are patched, but want to demonstrate that you are still vulnerable, you can use this command:
env X='() { (a)=>' bash -c “echo date”;
This command will return an error on a patched system, but it will still create a file with the output of date
in a file called “echo”.
ICS-CERT encourages asset owners to take additional defensive measures to protect against this and other cybersecurity risks.
ICS-CERT also provides a section for control systems security recommended practices on the ICS-CERT web page at http://ics-cert.us-cert.gov/content/recommended-practices. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies. ICS-CERT reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.
Additional mitigation guidance and recommended practices are publicly available in the ICS‑CERT Technical Information Paper, ICS-TIP-12-146-01B—Targeted Cyber Intrusion Detection and Mitigation Strategies, that is available for download from the ICS-CERT web site (www.ics-cert.org).
Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to ICS-CERT for tracking and correlation against other incidents.
In addition, ICS-CERT recommends that users take the following measures to protect themselves from social engineering attacks:
centosnow.blogspot.com/2014/09/critical-bash-updates-for-centos-5.html
lists.centos.org/pipermail/centos/2014-September/146099.html
lists.gnu.org/archive/html/bug-bash/2014-09/threads.html
support.novell.com/security/cve/CVE-2014-6271.html
tinyurl.com/p8fxk8e
tinyurl.com/q6218p2
www.ubuntu.com/usn/usn-2362-1/
bugzilla.redhat.com/show_bug.cgi?id=CVE-2014-6271
lists.debian.org/debian-security-announce/2014/msg00220.html
public.govdelivery.com/accounts/USDHSCISA/subscriber/new?topic_id=USDHSCISA_138
securityblog.redhat.com/2014/09/24/bash-specially-crafted-environment-variables-code-injection-attack/
twitter.com/CISAgov
twitter.com/intent/tweet?text=Bash%20Command%20Injection%20Vulnerability%20%28Update%20A%29+https://www.cisa.gov/news-events/ics-advisories/icsa-14-269-01a
www.cert.gov.uk/resources/alerts/update-bash-vulnerability-aka-shellshock/
www.debian.org/security/2014/dsa-3032
www.dhs.gov
www.dhs.gov/foia
www.dhs.gov/performance-financial-reports
www.facebook.com/CISA
www.facebook.com/sharer/sharer.php?u=https://www.cisa.gov/news-events/ics-advisories/icsa-14-269-01a&title=Bash%20Command%20Injection%20Vulnerability%20%28Update%20A%29
www.instagram.com/cisagov
www.linkedin.com/company/cybersecurity-and-infrastructure-security-agency
www.linkedin.com/sharing/share-offsite/?url=https://www.cisa.gov/news-events/ics-advisories/icsa-14-269-01a
www.oig.dhs.gov/
www.surveymonkey.com/r/CISA-cyber-survey?product=https://www.cisa.gov/news-events/ics-advisories/icsa-14-269-01a
www.usa.gov/
www.whitehouse.gov/
www.youtube.com/@cisagov
mailto:?subject=Bash%20Command%20Injection%20Vulnerability%20%28Update%20A%29&body=www.cisa.gov/news-events/ics-advisories/icsa-14-269-01a
9.8 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8 High
AI Score
Confidence
High
10 High
CVSS2
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
AV:N/AC:L/Au:N/C:C/I:C/A:C
0.976 High
EPSS
Percentile
100.0%