Bug 2545174 (CVE-2026-88812)

Summary:	CVE-2026-88812 xorg-x11-server: xwayland: xorg-x11-server: Arbitrary code execution via double-free in XKB geometry handling
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	rhel-process-autobot, security-response-team, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the X.Org X Server and XWayland. An error handling issue in the X Keyboard Extension (XKB) geometry processing fails to clear a memory pointer after an allocation failure, leading to a double-free condition during cleanup. A local user can exploit this vulnerability by sending a specially crafted request to the display server. This can cause memory corruption, potentially resulting in a Denial of Service (DoS) or arbitrary code execution with elevated privileges.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Deadline:	2026-10-07

Description OSIDB Bzimport 2026-10-02 13:00:28 UTC

_CheckSetDoodad() allocates doodad->text.text via _GetCountedString()
and then attempts to allocate doodad->text.font. If the font string
allocation fails (e.g. because the font string length extends past
the request boundary), the error handler frees doodad->text.text but
does not NULL the pointer. The doodad was already added to the geometry
by XkbAddGeomDoodad() before the string allocations, so when
XkbFreeGeometry() runs cleanup, _XkbClearDoodad() frees the same
dangling pointer again, resulting in a double-free.

NULL the pointer after freeing it to prevent the double-free.

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

ZDI-CAN-31221