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Olivier Fourdan fb6dd658d7 Cursor: Refuse to free the root cursor
If a cursor reference count drops to 0, the cursor is freed.

The root cursor however is referenced with a specific global variable,
and when the root cursor is freed, the global variable may still point
to freed memory.

Make sure to prevent the rootCursor from being explicitly freed by a
client.

CVE-2025-26594, ZDI-CAN-25544

This vulnerability was discovered by:
Jan-Niklas Sohn working with Trend Micro Zero Day Initiative

v2: Explicitly forbid XFreeCursor() on the root cursor (Peter Hutterer
<peter.hutterer@who-t.net>)
v3: Return BadCursor instead of BadValue (Michel Dänzer
<michel@daenzer.net>)

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Suggested-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1828>
(cherry picked from commit 01642f263f)
2026-01-25 10:40:00 -08:00
.gitlab-ci ci: update XTS to a commit that doesn't require -fcommon workaround 2026-01-25 10:40:00 -08:00
composite composite: drop swapping request length fields 2026-01-25 10:39:58 -08:00
config linux: Fix BUS_PLATFORM detection for non-PCI devices 2026-01-25 10:40:00 -08:00
damageext damage: drop swapping request length fields 2026-01-25 10:39:59 -08:00
dbe dbe: fix byte swapping in SProcDbeSwapBuffers() 2026-01-25 10:40:00 -08:00
dix Cursor: Refuse to free the root cursor 2026-01-25 10:40:00 -08:00
doc doc: drop removed PaintWindowBackground() and PaintWindowBorder() 2026-01-25 10:40:00 -08:00
dri3 dri3: drop swapping request length fields 2026-01-25 10:39:59 -08:00
exa Move sizeof to second argument in calloc calls 2026-01-25 10:39:55 -08:00
fb Revert "fb: Declare wfbFinishScreenInit, wfbScreenInit for !FB_ACCESS_WRAPPER" 2026-01-25 10:39:58 -08:00
glamor glamor: explicitly draw endpoints of line segments 2026-01-25 10:40:00 -08:00
glx glx: DoQueryContext(): explicitly use reply buf type defined by spec 2026-01-25 10:39:58 -08:00
hw xwin: don't need NULL check before free() 2026-01-25 10:40:00 -08:00
include drop not needed includes of geext.h 2026-01-25 10:40:00 -08:00
man Xserver.man: Note that -byteswappedclients is the default in this release 2026-01-19 12:32:23 -08:00
mi mi: miexpose: fix FTBS w/ rootless helper 2026-01-25 10:40:00 -08:00
miext miext: rootless: fix unused variables 2026-01-25 10:40:00 -08:00
os os: drop upstart specific SIGSTOP signaling logic 2026-01-25 10:40:00 -08:00
present present: need to include geext.h 2026-01-25 10:40:00 -08:00
pseudoramiX pseudoramiX: drop swapping request length fields 2026-01-25 10:39:58 -08:00
randr randr: drop now obsolete swap procs 2026-01-25 10:39:59 -08:00
record record: drop swapping request length fields 2026-01-25 10:39:58 -08:00
render render: drop swapping request length fields 2026-01-25 10:39:59 -08:00
test test: sync: don't use VLA 2026-01-25 10:40:00 -08:00
Xext Xext: dpms: need to include geext.h 2026-01-25 10:40:00 -08:00
xfixes xfixes: drop swapping request length fields 2026-01-25 10:39:58 -08:00
Xi drop not needed includes of geext.h 2026-01-25 10:40:00 -08:00
xkb xkb: drop swapping request length fields 2026-01-25 10:39:58 -08:00
.appveyor.yml appveyor: Add libxcvt build dep 2021-11-04 13:03:25 +00:00
.dir-locals.el .dir-locals.el: Add missing final newline 2019-10-01 17:05:28 +00:00
.git-blame-ignore-revs Ignore the coding style change commit during git blame 2026-01-25 10:39:58 -08:00
.gitignore Clean up the .gitignore file 2024-01-12 00:50:24 +00:00
.gitlab-ci.yml ci: update freebsd builder image 2026-01-25 10:40:00 -08:00
.mailmap Add a .mailmap file to canonicalize author names and emails 2023-03-15 18:10:51 +00:00
.travis.yml travis: Add OSX meson build to matrix 2019-05-02 15:42:58 +00:00
COPYING modesetting: Merge modesetting's COPYING into the xserver's. 2014-09-15 12:46:02 -07:00
meson.build meson.build: enable VLA warning 2026-01-25 10:40:00 -08:00
meson_options.txt os: drop SUN-DES-1 authentication 2026-01-25 10:39:53 -08:00
README.md Fix spelling/wording issues 2020-07-05 13:07:33 -07:00
xorg-server.m4 xorg-server.m4: just all cflags instead of just sdkdir 2018-09-20 20:12:24 +01:00
xorg-server.pc.in xfree86: link modules against Xorg symbols on Cygwin 2012-04-05 21:57:07 -05:00
xserver.ent.in doc: relocate xserver.ent in the package root directory 2011-05-14 11:22:26 -07:00

X Server

The X server accepts requests from client applications to create windows, which are (normally rectangular) "virtual screens" that the client program can draw into.

Windows are then composed on the actual screen by the X server (or by a separate composite manager) as directed by the window manager, which usually communicates with the user via graphical controls such as buttons and draggable titlebars and borders.

For a comprehensive overview of X Server and X Window System, consult the following article: https://en.wikipedia.org/wiki/X_server

All questions regarding this software should be directed at the Xorg mailing list:

https://lists.freedesktop.org/mailman/listinfo/xorg

The primary development code repository can be found at:

https://gitlab.freedesktop.org/xorg/xserver

For patch submission instructions, see:

https://www.x.org/wiki/Development/Documentation/SubmittingPatches

As with other projects hosted on freedesktop.org, X.Org follows its Code of Conduct, based on the Contributor Covenant. Please conduct yourself in a respectful and civilized manner when using the above mailing lists, bug trackers, etc:

https://www.freedesktop.org/wiki/CodeOfConduct