The Citrix EPA ActiveX control (aka the "endpoint checking control" or CCAOControl Object) before 4.5.0.0 in npCtxCAO.dll in Citrix Access Gateway Standard Edition before 4.5.5 and Advanced Edition before 4.5 HF1 allows remote attackers to download and execute arbitrary programs onto a client system.
The web authentication form in the NT4 authentication component in Citrix Access Gateway Enterprise Edition 9.2-49.8 and earlier, and the NTLM authentication component in Access Gateway Standard and Advanced Editions before Access Gateway 5.0, allows attackers to execute arbitrary commands via shell metacharacters in the password field.