This was fixed in the trunk in r53526 about a year ago following
issue1507247. I did not backport it to 2.5 at that time, because it
would have changed existing behaviour. If there are no objections I
could do this now.

The os.mkdir() call in TarFile.makedir() uses the default mode, but the
real mode from the TarInfo object is applied two instructions later in
TarFile._extract_member(). I have nothing against using 0700 in
TarFile.makedir().

The os.makedirs() call in _extract_member() (trunk) is fine. It creates
missing directories that are not part of the archive with default
permissions, that is mode 0777 with the current umask masked out.

I attached a patchset against the release25-maint branch and the trunk
that is supposed to fix the issue and harmonizes the code between the
two versions.