eced7e74ca
CheckKeyTypes validates incoming key type definitions from XkbSetMap
requests but does not enforce an upper bound on numLevels. A client can set
numLevels up to 255 on a non-canonical key type, which is stored in the
server's type table.
When ChangeKeyboardMapping later triggers XkbUpdateKeyTypesFromCore, the
function XkbKeyTypesForCoreSymbols computes groupsWidth from num_levels and
uses the XKB_OFFSET(g, l) = (g * groupsWidth) + l macro to index into
tsyms[], a stack-allocated buffer of XkbMaxSymsPerKey (252) entries. With
num_levels=255, groupsWidth=255, and indices reach up to 3*255+254 = 1019,
overflowing the 252-element stack buffer by 767 KeySym-sized entries.
Fix by rejecting numLevels values greater than XkbMaxShiftLevel (63) in
CheckKeyTypes, alongside the existing lower-bound check for numLevels < 1.
This vulnerability was discovered by:
Anonymous working with TrendAI Zero Day Initiative
ZDI-CAN-30160
Assisted-by: Claude:claude-opus-4-6
(cherry picked from commit
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| composite | ||
| config | ||
| damageext | ||
| dbe | ||
| dix | ||
| doc | ||
| dri3 | ||
| exa | ||
| fb | ||
| glamor | ||
| glx | ||
| hw | ||
| include | ||
| m4 | ||
| man | ||
| mi | ||
| miext | ||
| os | ||
| present | ||
| pseudoramiX | ||
| randr | ||
| record | ||
| render | ||
| test | ||
| Xext | ||
| xfixes | ||
| Xi | ||
| xkb | ||
| .appveyor.yml | ||
| .dir-locals.el | ||
| .gitignore | ||
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| autogen.sh | ||
| configure.ac | ||
| COPYING | ||
| devbook.am | ||
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| Makefile.am | ||
| manpages.am | ||
| meson.build | ||
| meson_options.txt | ||
| 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: