Bug 2485380 (CVE-2026-50256)

Summary:	CVE-2026-50256 xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in font alias resolution due to libXfont2 name length mismatch
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, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X server and the libXfont2 library's maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2's alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks. This may be used to crash the server, or for privilege escalation if the X server runs as root.	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:

Description OSIDB Bzimport 2026-06-05 07:38:24 UTC

A mismatch between the X server and the libXfont2 library's maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2's alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks.

Any X client that can connect to the server can trigger this issue. This may be used to crash the server, or for privilege escalation if the X server runs as root.

Components affected: xorg-x11-server, xorg-x11-server-Xwayland
Versions affected: xorg-x11-server <= 21.1.22, xorg-x11-server-Xwayland <= 24.1.9

Fixed upstream in xorg-server-21.1.23 and xwayland-24.1.12.
Fix: https://gitlab.freedesktop.org/xorg/xserver/-/commit/bb5158f962dc935e58ef8b4b5fcb31be201a6e07

Reported via ZDI-CAN-30136 (Trend Micro Zero Day Initiative). Tracking: PSIRTSUPT-16950.

Comment 1 errata-xmlrpc 2026-06-17 12:06:36 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:26562 https://access.redhat.com/errata/RHSA-2026:26562

Comment 2 errata-xmlrpc 2026-06-17 14:49:28 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:26590 https://access.redhat.com/errata/RHSA-2026:26590

Comment 3 errata-xmlrpc 2026-06-17 15:41:06 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:26610 https://access.redhat.com/errata/RHSA-2026:26610

Comment 4 errata-xmlrpc 2026-06-17 17:49:07 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:26709 https://access.redhat.com/errata/RHSA-2026:26709

Comment 5 errata-xmlrpc 2026-06-22 02:25:13 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:26566 https://access.redhat.com/errata/RHSA-2026:26566

Comment 6 errata-xmlrpc 2026-06-24 10:22:45 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:28923 https://access.redhat.com/errata/RHSA-2026:28923

Comment 7 errata-xmlrpc 2026-06-25 12:55:40 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:29844 https://access.redhat.com/errata/RHSA-2026:29844

Comment 8 errata-xmlrpc 2026-07-07 05:59:11 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7 Extended Lifecycle Support

Via RHSA-2026:36083 https://access.redhat.com/errata/RHSA-2026:36083

Comment 9 errata-xmlrpc 2026-07-07 06:09:05 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:36086 https://access.redhat.com/errata/RHSA-2026:36086

Comment 10 errata-xmlrpc 2026-07-07 06:19:08 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:36087 https://access.redhat.com/errata/RHSA-2026:36087

Comment 11 errata-xmlrpc 2026-07-07 06:33:45 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:36085 https://access.redhat.com/errata/RHSA-2026:36085

Comment 12 errata-xmlrpc 2026-07-08 09:11:57 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:36633 https://access.redhat.com/errata/RHSA-2026:36633

Comment 13 errata-xmlrpc 2026-07-08 09:22:44 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:36632 https://access.redhat.com/errata/RHSA-2026:36632

Comment 14 errata-xmlrpc 2026-07-08 09:33:41 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:36634 https://access.redhat.com/errata/RHSA-2026:36634

Comment 15 errata-xmlrpc 2026-07-08 14:32:58 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.8 Telecommunications Update Service

Via RHSA-2026:36768 https://access.redhat.com/errata/RHSA-2026:36768

Comment 16 errata-xmlrpc 2026-07-08 16:11:33 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On

Via RHSA-2026:36791 https://access.redhat.com/errata/RHSA-2026:36791

Comment 17 errata-xmlrpc 2026-07-08 16:19:39 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On

Via RHSA-2026:36792 https://access.redhat.com/errata/RHSA-2026:36792

Comment 18 errata-xmlrpc 2026-07-08 16:21:51 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:36798 https://access.redhat.com/errata/RHSA-2026:36798

Comment 19 errata-xmlrpc 2026-07-13 03:22:50 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.8 Telecommunications Update Service

Via RHSA-2026:38502 https://access.redhat.com/errata/RHSA-2026:38502

Comment 20 errata-xmlrpc 2026-07-13 09:28:20 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On

Via RHSA-2026:38810 https://access.redhat.com/errata/RHSA-2026:38810

Comment 21 errata-xmlrpc 2026-07-27 02:21:51 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:46377 https://access.redhat.com/errata/RHSA-2026:46377

Comment 22 errata-xmlrpc 2026-07-27 03:19:25 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On

Via RHSA-2026:46382 https://access.redhat.com/errata/RHSA-2026:46382

Comment 23 errata-xmlrpc 2026-07-27 03:27:58 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.8 Telecommunications Update Service

Via RHSA-2026:46385 https://access.redhat.com/errata/RHSA-2026:46385

Comment 24 errata-xmlrpc 2026-07-27 03:32:02 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:46392 https://access.redhat.com/errata/RHSA-2026:46392

Comment 25 errata-xmlrpc 2026-07-27 06:05:03 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:46456 https://access.redhat.com/errata/RHSA-2026:46456

Comment 26 errata-xmlrpc 2026-07-27 06:19:09 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On

Via RHSA-2026:46460 https://access.redhat.com/errata/RHSA-2026:46460

Comment 27 errata-xmlrpc 2026-07-27 09:39:08 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7 Extended Lifecycle Support

Via RHSA-2026:46473 https://access.redhat.com/errata/RHSA-2026:46473

Comment 28 errata-xmlrpc 2026-08-03 02:49:08 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6 Extended Lifecycle Support  - EXTENSION

Via RHSA-2026:49519 https://access.redhat.com/errata/RHSA-2026:49519