According to [1] mailinabox seems to be not affected.
[1] https://github.com/mail-in-a-box/mailinabox/issues/1663#issu...
[1] https://github.com/mail-in-a-box/mailinabox/issues/1663#issu...
That's not to say another similar exploit might have worked a different way. Luckily that bug is patched now.