Bug 2545177 (CVE-2026-93523) - CVE-2026-93523 xorg-x11-server: xorg-x11-server: Out-of-bounds write via unvalidated modifier in ProcXIPassiveUngrabDevice
Summary: CVE-2026-93523 xorg-x11-server: xorg-x11-server: Out-of-bounds write via unva...
Keywords:
Status: NEW
Alias: CVE-2026-93523
Deadline: 2026-10-07
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-10-02 13:03 UTC by OSIDB Bzimport
Modified: 2026-10-08 09:34 UTC (History)
3 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


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Description OSIDB Bzimport 2026-10-02 13:03:29 UTC
ProcXIPassiveUngrabDevice() passes client-supplied modifier values
directly to DeletePassiveGrabFromList() without validating them.

DeletePassiveGrabFromList() may reach DeleteDetailFromMask() which uses
BITCLEAR(mask, modifier). The mask is allocated as 8 Mask words (256
bits). A modifier value > 255 causes BITCLEAR to index mask[modifier>>5]
past the allocation, resulting in a controlled single-bit-clear at an
attacker-chosen heap offset.

Add the same modifier validation that CheckGrabValues() uses: reject
modifiers that are not XIAnyModifier and have bits set outside
AllModifiersMask.

This vulnerability was discovered by:
  Anonymous working with TrendAI Zero Day Initiative

ZDI-CAN-32366


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