USN-5956-1: PHPMailer vulnerabilities

Dawid Golunski discovered that PHPMailer was not properly escaping user
input data used as arguments to functions executed by the system shell. An
attacker could possibly use this issue to execute arbitrary code. This
issue only affected Ubuntu 16.04 ESM. (CVE-2016-10033, CVE-2016-10045)

It was discovered that PHPMailer was not properly escaping characters
in certain fields of the code_generator.php example code. An attacker
could possibly use this issue to conduct cross-site scripting (XSS)
attacks. This issue was only fixed in Ubuntu 16.04 ESM and Ubuntu 18.04
ESM. (CVE-2017-11503)

Yongxiang Li discovered that PHPMailer was not properly converting
relative paths provided as user input when adding attachments to messages,
which could lead to relative image URLs being treated as absolute local
file paths and added as attachments. An attacker could possibly use this
issue to access unauthorized resources and expose sensitive information.
This issue only affected Ubuntu 16.04 ESM. (CVE-2017-5223)

Sehun Oh discovered that PHPMailer was not properly processing untrusted
non-local file attachments, which could lead to an object injection. An
attacker could possibly use this issue to execute arbitrary code. This
issue only affected Ubuntu 16.04 ESM. (CVE-2018-19296)

Elar Lang discovered that PHPMailer was not properly escaping file
attachment names, which could lead to a misinterpretation of file types
by entities processing the message. An attacker could possibly use this
issue to bypass attachment filters. This issue was only fixed in Ubuntu
16.04 ESM and Ubuntu 20.04 ESM. (CVE-2020-13625)

It was discovered that PHPMailer was not properly handling callables in
its validateAddress function, which could result in untrusted code being
called should the global namespace contain a function called 'php'. An
attacker could possibly use this issue to execute arbitrary code. This
issue was only fixed in Ubuntu 20.04 ESM and Ubuntu 22.04 ESM.
(CVE-2021-3603)