Heap-based buffer overflow in the sql_prepare_where function (contrib/mod_sql.c) in ProFTPD before 1.3.3d, when mod_sql is enabled, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted username containing substitution tags, which are not properly handled during construction of an SQL query.
http://www.vupen.com/english/advisories/2011/0331
http://www.vupen.com/english/advisories/2011/0248
http://www.securityfocus.com/bid/44933
http://www.mandriva.com/security/advisories?name=MDVSA-2011:023
http://www.debian.org/security/2011/dsa-2191
http://proftpd.org/docs/RELEASE_NOTES-1.3.3d
http://phrack.org/issues.html?issue=67&id=7#article
http://lists.fedoraproject.org/pipermail/package-announce/2011-January/053540.html
http://lists.fedoraproject.org/pipermail/package-announce/2011-January/053537.html