A Bash security update has been released for Ubuntu Linux 12.04 ESM. Ubuntu Extended Security Maintenance (ESM) is a paid security subscription provided by Canonical Ltd.

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Ubuntu Security Notice USN-4180-1
November 11, 2019

bash vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 12.04 ESM

Summary:

Bash could be made to crash or execute arbitrary code if it received
a specially crafted input.

Software Description:
- bash: GNU Bourne Again SHell

Details:

It was discovered that Bash incorrectly handled certain inputs.
An attacker could possibly use this issue to cause a crash or execute
arbitrary code.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 12.04 ESM:
bash 4.2-2ubuntu2.9

After a standard system update you need to restart Bash to make
all the necessary changes.

References:
https://usn.ubuntu.com/4180-1
CVE-2012-6711