#VU5295 Command injection in Bash - CVE-2014-6271

Vulnerability identifier: #VU5295

Vulnerability risk: Critical

CVSSv4.0: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:A/U:Red]

CVE-ID: CVE-2014-6271

CWE-ID: CWE-77

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
Bash
Universal components / Libraries / Scripting languages

Vendor: GNU

Description

The vulnerability allows a remote attacker to execute arbitrary commands on the target system.

The vulnerability exists due to incorrect parsing of environment variables. A remote attacker can execute arbitrary code on the target system 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.

Successful exploitation may allow an attacker to gain complete control over vulnerable system.

Exploitation example:

env x='() { :;}; echo vulnerable' bash -c "echo this is a test"

Note: this vulnerability was being actively exploited in the wild.

Mitigation
Update GNU Bash to version 4.3 bash43-027.

Vulnerable software versions

Bash: 1.14.0 - 4.3

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External links
https://ftp.gnu.org/gnu/bash/bash-4.3-patches/bash43-027

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

Yes. This vulnerability is being exploited in the wild.