54c3d9fad0
CheckKeyTypes computes nMaps = firstType + nTypes from client-controlled
request fields when XkbSetMapResizeTypes is set. This value is used to
index mapWidths[], a stack-allocated CARD8 array of XkbMaxLegalKeyCode + 1
(256) elements. No upper bound is enforced on nMaps.
An attacker can first send SetMap(firstType=0, nTypes=255, ResizeTypes) to
set the server's num_types to 255, then send SetMap(firstType=255,
nTypes=10, ResizeTypes). The firstType > num_types check passes because
255 > 255 is false (the check uses > rather than >=). nMaps is then
computed as 265, and the loop writes mapWidths[255..264], overflowing 9
bytes past the stack buffer into adjacent stack variables (symsPerKey[]).
Fix by rejecting requests where firstType + nTypes would exceed the
mapWidths buffer size (XkbMaxLegalKeyCode + 1).
This vulnerability was discovered by:
Anonymous working with TrendAI Zero Day Initiative
ZDI-CAN-30161
Assisted-by: Claude:claude-opus-4-6
(cherry picked from commit
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| test | ||
| Xext | ||
| xfixes | ||
| Xi | ||
| xkb | ||
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| README.md | ||
| SECURITY.md | ||
| xorg-server.m4 | ||
| xorg-server.pc.in | ||
| xserver.ent.in | ||
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: