viewrq.php in nweb2fax 0.2.7 and earlier allows remote attackers to execute arbitrary code via shell metacharacters in the var_filename parameter in a (1) tif or (2) pdf format action.
Improper Neutralization of Special Elements used in an OS Command The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.