Heap corruption vulnerability in the "at" program allows local users to execute arbitrary code via a malformed execution time, which causes at to free the same memory twice.
https://exchange.xforce.ibmcloud.com/vulnerabilities/7909
http://www.redhat.com/support/errata/RHSA-2002-015.html
http://www.novell.com/linux/security/advisories/2002_003_at_txt.html
http://www.debian.org/security/2002/dsa-102
http://online.securityfocus.com/advisories/3969
http://online.securityfocus.com/advisories/3833