#VU5328 Off-by-one error in Bash - CVE-2014-7187

Vulnerability identifier: #VU5328

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-2014-7187

CWE-ID: CWE-193

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 code on the target system.

The weakness exists due to off-by-one-error when handling deeply nested flow control constructs. A remote attacker can trigger memory corruption and execute arbitrary code with privileges of the current user.

Exploitation example:

(for x in {1..200} ; do echo "for x$x in ; do :"; done; for x in {1..200} ; do echo done ; done) | bash ||
echo "CVE-2014-7187 vulnerable, word_lineno"

Successful exploitation results in arbitrary code execution on the vulnerable system.

Note: this vulnerability was being actively exploited.

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?

No. We are not aware of malware exploiting this vulnerability. However, a fully functional exploit for this vulnerability is available.