Animated cursors use a series of cursors that the client can set.
By default, the Xserver assumes at least one cursor is specified
while a client may actually pass no cursor at all.
That causes an out-of-bound read creating the animated cursor and a
crash of the Xserver:
| Invalid read of size 8
| at 0x5323F4: AnimCursorCreate (animcur.c:325)
| by 0x52D4C5: ProcRenderCreateAnimCursor (render.c:1817)
| by 0x52DC80: ProcRenderDispatch (render.c:1999)
| by 0x4A1E9D: Dispatch (dispatch.c:560)
| by 0x4B0169: dix_main (main.c:284)
| by 0x4287F5: main (stubmain.c:34)
| Address 0x59aa010 is 0 bytes after a block of size 0 alloc'd
| at 0x48468D3: reallocarray (vg_replace_malloc.c:1803)
| by 0x52D3DA: ProcRenderCreateAnimCursor (render.c:1802)
| by 0x52DC80: ProcRenderDispatch (render.c:1999)
| by 0x4A1E9D: Dispatch (dispatch.c:560)
| by 0x4B0169: dix_main (main.c:284)
| by 0x4287F5: main (stubmain.c:34)
|
| Invalid read of size 2
| at 0x5323F7: AnimCursorCreate (animcur.c:325)
| by 0x52D4C5: ProcRenderCreateAnimCursor (render.c:1817)
| by 0x52DC80: ProcRenderDispatch (render.c:1999)
| by 0x4A1E9D: Dispatch (dispatch.c:560)
| by 0x4B0169: dix_main (main.c:284)
| by 0x4287F5: main (stubmain.c:34)
| Address 0x8 is not stack'd, malloc'd or (recently) free'd
To avoid the issue, check the number of cursors specified and return a
BadValue error in both the proc handler (early) and the animated cursor
creation (as this is a public function) if there is 0 or less cursor.
CVE-2025-49175
This issue was discovered by Nils Emmerich <nemmerich@ernw.de> and
reported by Julian Suleder via ERNW Vulnerability Disclosure.
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: José Expósito <jexposit@redhat.com>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2024>
0885e0b262