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

Fixed packages 23

Vulnerabilities 3

• High 7.8
  CVE-2026-33999

  Xorg: xwayland: x.org x server: denial of service via integer underflow in xkb compatibility map handling

  A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violat…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Azure Linux Alpine
  Apr 23, 2026
• High 7.8
  CVE-2026-34001

  Xorg: xwayland: x.org x server: use-after-free vulnerability leads to server crash and potential memory corruption

  A flaw was found in the X.Org X server. This use-after-free vulnerability occurs in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function. An attacker with access to the X11 server can exploit this without user interaction, l…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Azure Linux Alpine
  Apr 23, 2026
• High 7.8
  CVE-2026-34003

  Xorg: xwayland: x.org x server: information exposure and denial of service via out-of-bounds memory access

  A flaw was found in the X.Org X server's XKB key types request validation. A local attacker could send a specially crafted request to the X server, leading to an out-of-bounds memory access vulnerability. This could result in the disclosure of sensitive infor…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Azure Linux Alpine
  Apr 23, 2026

References

• article
  https://access.redhat.com/security/updates/classification/#important
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2451106
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2451109
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2451113
• advisory
  https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_11388.json
• report
  https://access.redhat.com/security/cve/CVE-2026-33999
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-33999
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-33999
• report
  https://access.redhat.com/security/cve/CVE-2026-34001
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-34001
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-34001
• report
  https://access.redhat.com/security/cve/CVE-2026-34003
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-34003
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-34003