RHSA-2026:21742HighCVSS 7.8

Red Hat Security Advisory: xorg-x11-server security update

Published
May 28, 2026
Last Modified
November 5, 2026

🔗 CVE IDs covered (5)

CVE-2026-34001 →CVE-2026-34002 →CVE-2026-34003 →CVE-2026-33999 →CVE-2026-34000 →

📋 Description

CVE-2026-33999 — xorg: xwayland: X.Org X server: Denial of Service via integer underflow in XKB compatibility map handling CVE-2026-34000 — xwayland: xorg: X.Org X server: Information disclosure and denial of service via out-of-bounds read in XKB geometry processing. CVE-2026-34001 — xorg: xwayland: X.Org X server: Use-after-free vulnerability leads to server crash and potential memory corruption CVE-2026-34002 — xorg: xwayland: X.Org X server: Information disclosure or Denial of Service via out-of-bounds read in XKB modifier map handling CVE-2026-34003 — xorg: xwayland: X.Org X server: Information exposure and denial of service via out-of-bounds memory access

🎯 Affected products43

  • Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-0:1.20.11-18.el8_8.src as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-0:1.20.11-18.el8_8.src as a component of Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-Xdmx-0:1.20.11-18.el8_8.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xdmx-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xdmx-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-Xdmx-debuginfo-0:1.20.11-18.el8_8.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xdmx-debuginfo-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xdmx-debuginfo-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-Xephyr-0:1.20.11-18.el8_8.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xephyr-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xephyr-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-Xephyr-debuginfo-0:1.20.11-18.el8_8.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xephyr-debuginfo-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xephyr-debuginfo-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-Xnest-0:1.20.11-18.el8_8.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xnest-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xnest-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-Xnest-debuginfo-0:1.20.11-18.el8_8.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xnest-debuginfo-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xnest-debuginfo-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-Xorg-0:1.20.11-18.el8_8.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xorg-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xorg-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-Xorg-debuginfo-0:1.20.11-18.el8_8.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xorg-debuginfo-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xorg-debuginfo-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream TUS (v.8.8)
  • xorg-x11-server-Xvfb-0:1.20.11-18.el8_8.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • xorg-x11-server-Xvfb-0:1.20.11-18.el8_8.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.8.8)
  • +13 more not shown

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 Workaround: To mitigate this issue, restrict access to the X11 server. For remote access, disable X11 forwarding in SSH configurations if not required. Edit `/etc/ssh/sshd_config` and set `X11Forwarding no`. After modifying the configuration, restart the `sshd` service using `systemctl restart sshd`. Disabling X11 forwarding may impact remote graphical applications. Workaround: To mitigate this vulnerability, restrict access to the X11 server. On systems where a graphical environment is not required, consider disabling the X server entirely by setting the default system target to multi-user mode. For systems requiring the X server, ensure that X11 forwarding is disabled in SSH configurations if not explicitly needed, and restrict direct X11 connections to trusted users and networks through firewall rules. If changes are made to SSH configuration, the `sshd` service must be restarted. If the default system target is changed, a system reboot is required. Workaround: To mitigate this issue, restrict access to the X11 server to trusted users and networks. If the X.Org X server is not required, consider disabling or uninstalling it. For environments where the X server is essential, running X applications within a sandboxed environment can help reduce the attack surface. Workaround: To mitigate this vulnerability, restrict access to the X11 server. If the X.Org X server is not required on a system, consider disabling or uninstalling it. For systems where the X server is necessary, ensure that access is limited to trusted users and networks. This can involve configuring `xhost` or implementing firewall rules to restrict connections to the X server. Any changes to X server configuration or service status may require a restart of the X server for the mitigation to take effect, which will impact active graphical sessions. Workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

🔗 References (8)