Drush error on core update "corrupt (wrong md5 checksum)"
By looking at this drupal issue queue thread, https://www.drupal.org/node/1961304 , if you are using Drush Make and having problems try --no-cache option for your build.

Otherwise assure the downloaded Drupal version, or module, is readable by the Drush user. If drush cannot read the file then the md5 checksum cannot be run and Drush will report a corrupt file:


  @sobi3ch: this appears to be a permissions issue. If i'm reading the
  Drush output correctly,
  "md5_file(/var/www/vhosts/etcc.pl/drupal-7.38.tar.gz): failed to open
  stream: Permission denied" is saying the md5 checksum function is
  unable to open the file to validate the checksum on it, which causes
  drush to think the file has the wrong checksum.