During a routine vulnerability assessment, the following command was successful: echo "vrfy `perl -e `print "hi" x 500 ` ` " | nc www.company.com 25 Which of the following vulnerabilities is being exploited? 

Answer options:

A. Buffer overflow directed at a specific host MTA
B. SQL injection directed at a web server
C. Cross-site scripting directed at www.company.com
D. Race condition in a UNIX shell script

A