The expansion of '\h' in the prompt string in bash 4.3 allows remote authenticated users to execute arbitrary code via shell metacharacters placed in 'hostname' of a machine.

Affected: Ubuntu:14.04:LTS: bash, Ubuntu:16.04:LTS: bash

Bernd Dietzel discovered that Bash incorrectly expanded the hostname when displaying the prompt. If a remote attacker were able to modify a hostname, this flaw could be exploited to execute arbitrary code. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS and Ubuntu 16.10. (CVE-2016-0634)

It was discovered that Bash incorrectly handled the SHELLOPTS and PS4 environment variables. A local attacker could use this issue to execute arbitrary code with root privileges. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS and Ubuntu 16.10. (CVE-2016-7543)

It was discovered that Bash incorrectly handled the popd command. A remote attacker could possibly use this issue to bypass restricted shells. (CVE-2016-9401)

It was discovered that Bash incorrectly handled path autocompletion. A local attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 17.04. (CVE-2017-5932)