GNU Bourne-Again Shell (Bash) Arbitrary Code Execution
CVE-2014-6271 is a critical-severity improper neutralization of special elements used in an OS command vulnerability in Bash from GNU, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Bash versions: 4.3 and earlier. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on January 28, 2022, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Eos to 4.9.12 or 4.10.9 or 4.11.11 or 4.12.9, whichever matches your release line, or a later version.
- Update Qts to 4.1.1 or a later version.
- Update Software Defined Network For Virtual Environments to 1.2.1 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on jvn.jp for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| GNU | Bash | 4.3 and earlier | Not stated |
| Arista | Eos | 4.9.0 up to, but not including, 4.9.12; 4.10.0 up to, but not including, 4.10.9; 4.11.0 up to, but not including, 4.11.11; 4.12.0 up to, but not including, 4.12.9; 4.13.0 up to, but not including, 4.13.9; 4.14.0 up to, but not including, 4.14.4f | 4.9.12, 4.10.9, 4.11.11, 4.12.9, 4.13.9, 4.14.4f |
| Oracle | Linux | 4; 5; 6 | Not stated |
| QNAP | Qts | before 4.1.1; 4.1.1 | 4.1.1 |
| Mageia | Mageia | 3.0; 4.0 | Not stated |
| Red Hat | Gluster Storage Server For On-premise | 2.1 | Not stated |
| Red Hat | Virtualization | 3.4 | Not stated |
| Red Hat | Enterprise Linux | 4.0; 5.0; 6.0; 7.0 | Not stated |
| Red Hat | Enterprise Linux Desktop | 5.0; 6.0; 7.0 | Not stated |
| Red Hat | Enterprise Linux EUS | 5.9; 6.4; 6.5; 7.3; 7.4; 7.5; 7.6; 7.7 | Not stated |
| Red Hat | Enterprise Linux For IBM Z Systems | 5.9_s390x; 6.4_s390x; 6.5_s390x; 7.3_s390x; 7.4_s390x; 7.5_s390x; 7.6_s390x; 7.7_s390x | Not stated |
| Red Hat | Enterprise Linux For Power Big Endian | 5.0_ppc; 5.9_ppc; 6.0_ppc64; 6.4_ppc64; 7.0_ppc64 | Not stated |
| Red Hat | Enterprise Linux For Power Big Endian EUS | 6.5_ppc64; 7.3_ppc64; 7.4_ppc64; 7.5_ppc64; 7.6_ppc64; 7.7_ppc64 | Not stated |
| Red Hat | Enterprise Linux For Scientific Computing | 6.0; 7.0 | Not stated |
| Red Hat | Enterprise Linux Server | 5.0; 6.0; 7.0 | Not stated |
| Red Hat | Enterprise Linux Server AUS | 5.6; 5.9; 6.2; 6.4; 6.5; 7.3; 7.4; 7.6; and 1 more ranges | Not stated |
| Red Hat | Enterprise Linux Server From Rhui | 5.0; 6.0; 7.0 | Not stated |
| Red Hat | Enterprise Linux Server TUS | 6.5; 7.3; 7.6; 7.7 | Not stated |
| Red Hat | Enterprise Linux Workstation | 5.0; 6.0; 7.0 | Not stated |
| SUSE | Studio Onsite | 1.3 | Not stated |
| openSUSE | Opensuse | 12.3; 13.1; 13.2 | Not stated |
| SUSE | Linux Enterprise Desktop | 11; 12 | Not stated |
| SUSE | Linux Enterprise Server | 10; 11; 12 | Not stated |
| SUSE | Linux Enterprise Software Development Kit | 11; 12 | Not stated |
| Debian | Debian Linux | 7.0 | Not stated |
Version data comes from NVD's product matching; 35 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 3.1 | 9.8 | Critical | CISA (ADP) |
| CVSS 2.0 | 10.0 | High | NVD |
Official description
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, as demonstrated by vectors involving the ForceCommand feature in OpenSSH sshd, the mod_cgi and mod_cgid modules in the Apache HTTP Server, scripts executed by unspecified DHCP clients, and other situations in which setting the environment occurs across a privilege boundary from Bash execution, aka "ShellShock." NOTE: the original fix for this issue was incorrect; CVE-2014-7169 has been assigned to cover the vulnerability that is still present after the incorrect fix.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements used in an OS Command
The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.
How developers prevent this class of flaw
- If at all possible, use library calls rather than external processes to recreate the desired functionality.
- For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
More Improper Neutralization of Special Elements used in an OS Command vulnerabilities (CWE-78)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- jvn.jp/en/jp/JVN55667175/index.html
- jvndb.jvn.jp/jvndb/JVNDB-2014-000126Third Party Advisory, VDB Entry
- packetstormsecurity.com/files/128517/VMware-Security-Advisory-2014-0010.htmlExploit, Third Party Advisory, VDB Entry
Third-party and government advisories
- advisories.mageia.org/MGASA-2014-0388.htmlThird Party Advisory
- kb.juniper.net/InfoCenter/index?page=content&id=JSA10673Third Party Advisory
- linux.oracle.com/errata/ELSA-2014-1293.htmlThird Party Advisory
- linux.oracle.com/errata/ELSA-2014-1294.htmlThird Party Advisory
- lists.opensuse.org/opensuse-security-announce/2014-09/msg00028.htmlMailing List, Third Party Advisory
- lists.opensuse.org/opensuse-security-announce/2014-09/msg00029.htmlMailing List, Third Party Advisory
- lists.opensuse.org/opensuse-security-announce/2014-09/msg00034.htmlMailing List, Third Party Advisory
- lists.opensuse.org/opensuse-security-announce/2014-09/msg00037.htmlMailing List, Third Party Advisory
- lists.opensuse.org/opensuse-security-announce/2014-09/msg00040.htmlMailing List, Third Party Advisory
- lists.opensuse.org/opensuse-security-announce/2014-09/msg00044.htmlMailing List, Third Party Advisory
- lists.opensuse.org/opensuse-security-announce/2014-09/msg00049.htmlMailing List, Third Party Advisory
- lists.opensuse.org/opensuse-security-announce/2014-10/msg00004.htmlMailing List, Third Party Advisory
- lists.opensuse.org/opensuse-updates/2014-10/msg00023.htmlMailing List, Third Party Advisory
- lists.opensuse.org/opensuse-updates/2014-10/msg00025.htmlMailing List, Third Party Advisory
- marc.info/?l=bugtraq&m=141216207813411&w=2Mailing List, Third Party Advisory
Technical write-ups (may include proof of concept)
- lcamtuf.blogspot.com/2014/09/quick-notes-about-bash-bug-its-impact.htmlExploit, Issue Tracking, Third Party Advisory
- packetstormsecurity.com/files/128567/CA-Technologies-GNU-Bash-Shellshock.htmlExploit, Third Party Advisory, VDB Entry
- packetstormsecurity.com/files/128573/Apache-mod_cgi-Remote-Command-Execution.htmlExploit, Third Party Advisory, VDB Entry
- packetstormsecurity.com/files/137376/IPFire-Bash-Environment-Variable-Injection-Shellshock.htmlExploit, Third Party Advisory, VDB Entry
Other vulnerabilities in Bash
- 10.0 High severity
GNU Bash OS Command Injection Exploited
- 9.8 Critical severity
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