Multiple stack-based buffer overflows in the HMI application in DATAC RealFlex RealWin 2.1 (Build 6.1.10.10) and earlier allow remote attackers to execute arbitrary code via (1) a long username in an On_FC_CONNECT_FCS_LOGIN packet and crafted (2) On_FC_CTAGLIST_FCS_CADDTAG (3) On_FC_CTAGLIST_FCS_CDELTAG (4) On_FC_CTAGLIST_FCS_ADDTAGMS (5) On_FC_RFUSER_FCS_LOGIN (6) unspecified \On_FC_BINFILE_FCS_*FILE\ (7) On_FC_CGETTAG_FCS_GETTELEMETRY (8) On_FC_CGETTAG_FCS_GETCHANNELTELEMETRY (9) On_FC_CGETTAG_FCS_SETTELEMETRY (10) On_FC_CGETTAG_FCS_SETCHANNELTELEMETRY and (11) On_FC_SCRIPT_FCS_STARTPROG packets to port 910.