XScreenSaver 5.45 can be bypassed if the machine has more than ten disconnectable video outputs. A buffer overflow in update_screen_layout() allows an attacker to bypass the standard screen lock authentication mechanism by crashing XScreenSaver. The attacker must physically disconnect many video outputs.

The Debian xscreensaver 5.42+dfsg1-1 package for XScreenSaver has cap_net_raw enabled for the /usr/libexec/xscreensaver/sonar file, which allows local users to gain privileges because this is arguably incompatible with the design of the Mesa 3D Graphics library dependency.

xscreensaver before 5.14 crashes during activation and leaves the screen unlocked when in Blank Only Mode and when DPMS is disabled, which allows local attackers to access resources without authentication.

mate-screensaver before 1.20.2 in MATE Desktop Environment allows physically proximate attackers to view screen content and possibly control applications. By unplugging and re-plugging or power-cycling external output devices (such as additionally attached graphical outputs via HDMI, VGA, DVI, etc.) the content of a screensaver-locked session can be revealed. In some scenarios, the attacker can execute applications, such as by clicking with a mouse.

Untrusted search path vulnerability in screensaver installers (jasdf_01.exe, jasdf_02.exe, jasdf_03.exe, jasdf_04.exe, jasdf_05.exe, scramble_setup.exe, clock_01_setup.exe, clock_02_setup.exe) available prior to May 25, 2017 allows an attacker to gain privileges via a Trojan horse DLL in an unspecified directory.

driver/subprocs.c in XScreenSaver before 5.34 does not properly perform an internal consistency check, which allows physically proximate attackers to bypass the lock screen by hot swapping monitors.

The default configuration in gnome-screensaver 3.5.4 through 3.6.0 sets the AutostartCondition line to fallback mode in the .desktop file, which prevents the program from starting automatically after login and allows physically proximate attackers to bypass screen locking and access an unattended workstation.

gnome-screensaver 3.4.x before 3.4.4 and 3.5.x before 3.5.4, when multiple screens are used, only locks the screen with the active focus, which allows physically proximate attackers to bypass screen locking and access an unattended workstation.

gdk/gdkwindow.c in GTK+ before 2.18.5, as used in gnome-screensaver before 2.28.1, performs implicit paints on windows of type GDK_WINDOW_FOREIGN, which triggers an X error in certain circumstances and consequently allows physically proximate attackers to bypass screen locking and access an unattended workstation by pressing the Enter key many times.

gnome-screensaver 2.14.3, 2.22.2, 2.27.x, 2.28.0, and 2.28.3, when the X configuration enables the extend screen option, allows physically proximate attackers to bypass screen locking, access an unattended workstation, and view half of the GNOME desktop by attaching an external monitor.