This security update addresses multiple high-severity vulnerabilities (CVSS 7.8) in the X.Org server and Xwayland, including stack buffer overflows and use-after-free conditions that could lead to privilege escalation or information disclosure. The vulnerabilities affect X.Org X Server versions prior to 21.1.23 and Xwayland versions prior to 24.1.12, specifically impacting Red Hat Enterprise Linux 7.0, 8.0, and 9.0. The fix requires applying the Red Hat-provided update for the `xorg-x11-server` package on the affected RHEL Extended Life Cycle and Advanced Mission Critical Update Support channels.
Red Hat Product Errata RHSA-2026:36791 - Security Advisory Issued: 2026-07-08 Updated: 2026-07-08 RHSA-2026:36791 - Security Advisory Overview Updated Packages Synopsis Important: xorg-x11-server security update Type/Severity Security Advisory: Important Red Hat Lightspeed patch analysis Identify and remediate systems affected by this advisory. View affected systems Topic An update for xorg-x11-server is now available for Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section. Description X.Org is an open-source implementation of the X Window System. It provides the basic low-level functionality that full-fledged graphical user interfaces are designed upon. Security Fix(es): xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in font alias resolution due to libXfont2 name length mismatch (CVE-2026-50256) xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free in miSyncDestroyFence() (CVE-2026-50257) xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in XKB key types due to unchecked shift levels (CVE-2026-50258) xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in XKB SetMap request via mapWidths indexing (CVE-2026-50259) xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free in FreeCounter() (CVE-2026-50260) xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free in SyncChangeCounter() (CVE-2026-50261) xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: out-of-bounds read/write in GLX ChangeDrawableAttributes (CVE-2026-50262) xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free information disclosure in CreateSaverWindow() (CVE-2026-50263) xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: out-of-bounds heap write in DRI2 DRIGetBuffers/DRIGetBuffersWithFormat (CVE-2026-50264) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section. Solution For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 Affected Products Red Hat Enterprise Linux for x86_64 - Extended Life Cycle Long Life 8.6 x86_64 Red Hat Enterprise Linux Server - AUS 8.6 x86_64 Fixes BZ - 2485380 - 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 BZ - 2485382 - CVE-2026-50257 xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free in miSyncDestroyFence() BZ - 2485383 - CVE-2026-50258 xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in XKB key types due to unchecked shift levels BZ - 2485384 - CVE-2026-50259 xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: stack buffer overflow in XKB SetMap request via mapWidths indexing BZ - 2485385 - CVE-2026-50260 xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free in FreeCounter() BZ - 2485386 - CVE-2026-50261 xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free in SyncChangeCounter() BZ - 2485387 - CVE-2026-50262 xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: out-of-bounds read/write in GLX ChangeDrawableAttributes BZ - 2485388 - CVE-2026-50263 xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: use-after-free information disclosure in CreateSaverWindow() BZ - 2485389 - CVE-2026-50264 xorg-x11-server: xorg-x11-server-Xwayland: xorg-x11-server: out-of-bounds heap write in DRI2 DRIGetBuffers/DRIGetBuffersWithFormat CVEs CVE-2026-50256 CVE-2026-50257 CVE-2026-50258 CVE-2026-50259 CVE-2026-50260 CVE-2026-50261 CVE-2026-50262 CVE-2026-50263 CVE-2026-50264 References https://access.redhat.com/security/updates/classification/#important Note: More recent versions of these packages may be available. Click a package name for more details. Red Hat Enterprise Linux for x86_64 - Extended Life Cycle Long Life 8.6 SRPM xorg-x11-server-1.20.11-8.el8_6.src.rpm SHA-256: 99a2ce8082f0c7457fb08cd4f1855c820cbdb38fb3a686b7d0b0d5e4ea169219 x86_64 xorg-x11-server-Xdmx-1.20.11-8.el8_6.x86_64.rpm SHA-256: cd83f4fe09f5a7200629ce22375f32dc3ec95ae748a7d647c3ef7cb5cd8d5dd8 xorg-x11-server-Xdmx-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 5a3d807c6928b2753be6b97fc08a26e040d0cc77b2135d23300ed26f96f8d091 xorg-x11-server-Xephyr-1.20.11-8.el8_6.x86_64.rpm SHA-256: 874078a4e1c563b728b71a332615a6897905a04df114ea23af24ffa1ad280acd xorg-x11-server-Xephyr-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 36c2d0b3613caf383fae80e03b67949bbfeb835aaea28a7a0e5c0c4f28f17048 xorg-x11-server-Xnest-1.20.11-8.el8_6.x86_64.rpm SHA-256: f8734ab6f52fe9708f7892ace431baab4588acc45830d3bff20277320df5a96d xorg-x11-server-Xnest-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 7c5dbbe113da40746d69771accaa86e8868b7ab7530fed6f4ba1fe5b1a7da629 xorg-x11-server-Xorg-1.20.11-8.el8_6.x86_64.rpm SHA-256: e5aedd87eb2f1de9bbc3b296fab14b19c7e0c4605c9005737b863abed04cba2b xorg-x11-server-Xorg-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 71fa688871e7a20cca8845a4665a6628613cecad7fd8fda44cca96e517e228ca xorg-x11-server-Xvfb-1.20.11-8.el8_6.x86_64.rpm SHA-256: 484bb3274214f42ddebfc5bc01fb471d66f808263b4ef8af259e57b8fd14a477 xorg-x11-server-Xvfb-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: d44f643e352d53cb104c48590d2bc016a1b642feea79a5dc573ee073ca7342d5 xorg-x11-server-common-1.20.11-8.el8_6.x86_64.rpm SHA-256: f090b12979137f076c0f3627d590773cc149c992ad9d08875dfb1c0f97ea3795 xorg-x11-server-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 2ca5eebdb610bccdefe332eb67c7b358d9506ae2d083cd224c8194359c1ff707 xorg-x11-server-debugsource-1.20.11-8.el8_6.x86_64.rpm SHA-256: bec9c9403a316d7e18c2a3ff68ba267222d9909ff2bd9a5a03bebd00b9942582 Red Hat Enterprise Linux Server - AUS 8.6 SRPM xorg-x11-server-1.20.11-8.el8_6.src.rpm SHA-256: 99a2ce8082f0c7457fb08cd4f1855c820cbdb38fb3a686b7d0b0d5e4ea169219 x86_64 xorg-x11-server-Xdmx-1.20.11-8.el8_6.x86_64.rpm SHA-256: cd83f4fe09f5a7200629ce22375f32dc3ec95ae748a7d647c3ef7cb5cd8d5dd8 xorg-x11-server-Xdmx-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 5a3d807c6928b2753be6b97fc08a26e040d0cc77b2135d23300ed26f96f8d091 xorg-x11-server-Xephyr-1.20.11-8.el8_6.x86_64.rpm SHA-256: 874078a4e1c563b728b71a332615a6897905a04df114ea23af24ffa1ad280acd xorg-x11-server-Xephyr-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 36c2d0b3613caf383fae80e03b67949bbfeb835aaea28a7a0e5c0c4f28f17048 xorg-x11-server-Xnest-1.20.11-8.el8_6.x86_64.rpm SHA-256: f8734ab6f52fe9708f7892ace431baab4588acc45830d3bff20277320df5a96d xorg-x11-server-Xnest-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 7c5dbbe113da40746d69771accaa86e8868b7ab7530fed6f4ba1fe5b1a7da629 xorg-x11-server-Xorg-1.20.11-8.el8_6.x86_64.rpm SHA-256: e5aedd87eb2f1de9bbc3b296fab14b19c7e0c4605c9005737b863abed04cba2b xorg-x11-server-Xorg-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 71fa688871e7a20cca8845a4665a6628613cecad7fd8fda44cca96e517e228ca xorg-x11-server-Xvfb-1.20.11-8.el8_6.x86_64.rpm SHA-256: 484bb3274214f42ddebfc5bc01fb471d66f808263b4ef8af259e57b8fd14a477 xorg-x11-server-Xvfb-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: d44f643e352d53cb104c48590d2bc016a1b642feea79a5dc573ee073ca7342d5 xorg-x11-server-common-1.20.11-8.el8_6.x86_64.rpm SHA-256: f090b12979137f076c0f3627d590773cc149c992ad9d08875dfb1c0f97ea3795 xorg-x11-server-debuginfo-1.20.11-8.el8_6.x86_64.rpm SHA-256: 2ca5eebdb610bccdefe332eb67c7b358d9506ae2d083cd224c8194359c1ff707 xorg-x11-server-debugsource-1.20.11-8.el8_6.x86_64.rpm SHA-256: bec9c9403a316d7e18c2a3ff68ba267222d9909ff2bd9a5a03bebd00b9942582 The Red Hat security contact is secalert@redhat.com . More contact details at https://access.redhat.com/security/team/contact/ .