An issue was discovered in SDDM through 0.17.0. If configured with ReuseSession=true, the password is not checked for users with an already existing session. Any user with access to the system D-Bus can therefore unlock any graphical session. This is related to daemon/Display.cpp and helper/backend/PamBackend.cpp.
{ "binaries": [ { "binary_name": "sddm", "binary_version": "0.13.0-1ubuntu5" }, { "binary_name": "sddm-theme-circles", "binary_version": "0.13.0-1ubuntu5" }, { "binary_name": "sddm-theme-elarun", "binary_version": "0.13.0-1ubuntu5" }, { "binary_name": "sddm-theme-maldives", "binary_version": "0.13.0-1ubuntu5" }, { "binary_name": "sddm-theme-maui", "binary_version": "0.13.0-1ubuntu5" } ] }
{ "binaries": [ { "binary_name": "sddm", "binary_version": "0.17.0-1ubuntu7" }, { "binary_name": "sddm-theme-debian-elarun", "binary_version": "0.17.0-1ubuntu7" }, { "binary_name": "sddm-theme-debian-maui", "binary_version": "0.17.0-1ubuntu7" }, { "binary_name": "sddm-theme-elarun", "binary_version": "0.17.0-1ubuntu7" }, { "binary_name": "sddm-theme-maldives", "binary_version": "0.17.0-1ubuntu7" }, { "binary_name": "sddm-theme-maui", "binary_version": "0.17.0-1ubuntu7" }, { "binary_name": "sddm-theme-maya", "binary_version": "0.17.0-1ubuntu7" } ] }