Improper handling of session establishment errors in xrdp

xrdp is an open source remote desktop protocol (RDP) server. In versions prior to 0.9.23 improper handling of session establishment errors allows bypassing OS-level session restrictions. The auth_start_session function can return non-zero (1) value on, e.g., PAM error which may result in in session restrictions such as max concurrent sessions per user by PAM (ex ./etc/security/limits.conf) to be bypassed. Users (administrators) don't use restrictions by PAM are not affected. This issue has been addressed in release version 0.9.23. Users are advised to upgrade. There are no known workarounds for this issue.