Multiple off-by-one errors in the (1) MakeBigReq and (2) SetReqLen macros in include/X11/Xlibint.h in X11R6.x and libX11 before 1.6.0 allow remote attackers to have unspecified impact via a crafted request, which triggers a buffer overflow.

xkeyboard-config before 2.5 in X.Org before 7.6 enables certain XKB debugging functions by default, which allows physically proximate attackers to bypass an X screen lock via keyboard combinations that break the input grab.

Use-after-free vulnerability in the doImageText function in dix/dixfonts.c in the xorg-server module before 1.14.4 in X.Org X11 allows remote authenticated users to cause a denial of service (daemon crash) or possibly execute arbitrary code via a crafted ImageText request that triggers memory-allocation failure.

The ProcSetEventMask function in difs/events.c in the xfs font server for X.Org X11R6 through X11R6.6 and XFree86 before 3.3.3 calls the SendErrToClient function with a mask value instead of a pointer, which allows local users to cause a denial of service (memory corruption and crash) or obtain potentially sensitive information from memory via a SetEventMask request that triggers an invalid pointer dereference.

xscreensaver (aka Gnome-XScreenSaver) in Sun Solaris 9 and 10, OpenSolaris snv_109 through snv_122, and X11 6.4.1 on Solaris 8 does not properly handle Accessibility support, which allows local users to cause a denial of service (system hang) by locking the screen and then attempting to launch an Accessibility pop-up window, related to a regression in certain Solaris and OpenSolaris patches.

XScreenSaver in Sun Solaris 9 and 10, OpenSolaris before snv_120, and X11 6.4.1 for Solaris 8, when the Xorg or Xnewt server is used, allows physically proximate attackers to obtain sensitive information by reading popup windows, which are displayed even when the screen is locked, a different vulnerability than CVE-2009-1276.