Univention Corporate Server 4.3 erratum 75 (security)

This update addresses the following issues:
* w3m is prone to an infinite recursion flaw in HTMLlineproc0 because the
  feed_table_block_tag function in table.c does not prevent a negative indent
  value. (CVE-2018-6196)
* w3m is prone to a NULL pointer dereference flaw in formUpdateBuffer in
  form.c. (CVE-2018-6197)
* w3m does not properly handle temporary files when the ~/.w3m directory is
  unwritable, which allows a local attacker to craft a symlink attack to
  overwrite arbitrary files. (CVE-2018-6198)