This Red Hat security advisory addresses multiple high-severity vulnerabilities (CVSS 7.8) in the xorg-x11-server and xorg-x11-server-Xwayland packages, including stack buffer overflows, use-after-free flaws, and out-of-bounds read/write issues. The affected versions are x.org X Server prior to 21.1.23 and XWayland prior to 24.1.12, impacting Red Hat Enterprise Linux 7.0, 8.0, and 9.0. The fix requires applying the Red Hat-provided update for the specific supported branches (RHEL 8.4 Advanced Mission Critical Update Support and Extended Update Support Long-Life Add-On) as detailed in the advisory.
Red Hat Product Errata RHSA-2026:36792 - Security Advisory Issued: 2026-07-08 Updated: 2026-07-08 RHSA-2026:36792 - 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 8.4 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.4 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 8.4 x86_64 Red Hat Enterprise Linux Server - AUS 8.4 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 8.4 SRPM xorg-x11-server-1.20.10-5.el8_4.src.rpm SHA-256: d3760a03643f764ee04ba7f13f4885778745dcb2157fce9e65f79e501d41746f x86_64 xorg-x11-server-Xdmx-1.20.10-5.el8_4.x86_64.rpm SHA-256: 0e007eb3105194b05adb862e7ee55616d0d4ecb64e3437a0b92feb9a85fe8426 xorg-x11-server-Xdmx-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: 640711409d9d57d3dfd4364298b2496c0efc99db65f63141dc5184640466fbda xorg-x11-server-Xephyr-1.20.10-5.el8_4.x86_64.rpm SHA-256: 2955a2270f74253738171ec6a3974156999f0356906e6d078c4f7a495f471bcd xorg-x11-server-Xephyr-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: f443dc7e77b812f7c5f7102e9fdcfaba3eaee1dfe05b2df8400cddb65388979f xorg-x11-server-Xnest-1.20.10-5.el8_4.x86_64.rpm SHA-256: 6910c78dd4d15ed54b1cb56116d56d3fc8ae27520241bc833df5099d8c61e762 xorg-x11-server-Xnest-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: cb166840d4350b37b53a27a19ef8321db4f73e43024b23b7c80f1c5f43c0ef9d xorg-x11-server-Xorg-1.20.10-5.el8_4.x86_64.rpm SHA-256: b3c7cb2207d806b48cf982c9a07030147fc7951854f1bb5e61b63466dd4c9212 xorg-x11-server-Xorg-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: 2375f3e13c8725556ba6c65c74b982a7079b65e41ec6448b3298a87ff062e72b xorg-x11-server-Xvfb-1.20.10-5.el8_4.x86_64.rpm SHA-256: 6c037c872323341912bfbc7f1720b46e06c4d85c6238c43321a41e425c96d886 xorg-x11-server-Xvfb-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: cf3095758ef5de87cf8eedae1c9439ac8aa7cfbda270c3ba7597291fad1a7494 xorg-x11-server-Xwayland-1.20.10-5.el8_4.x86_64.rpm SHA-256: c10532f545ef577711902a5c67f89d67096ab812dab689d35e2d26432d7e738b xorg-x11-server-Xwayland-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: d884619e2ea6898f829ad15761b15ef103c7e06d840590ad97d9a3fd76b229a0 xorg-x11-server-common-1.20.10-5.el8_4.x86_64.rpm SHA-256: da474f457b72ff0635c0727f472493c4b0fdac7abe4a702c4a12ccaa29f7016c xorg-x11-server-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: 05a1ffd781bde0b96cb8a697f811ee19395a592ebccffbfb3903321f991f2316 xorg-x11-server-debugsource-1.20.10-5.el8_4.x86_64.rpm SHA-256: be6307d2d73233477be2406c5034f8912d856ac9f993603d07e0caba855424cb Red Hat Enterprise Linux Server - AUS 8.4 SRPM xorg-x11-server-1.20.10-5.el8_4.src.rpm SHA-256: d3760a03643f764ee04ba7f13f4885778745dcb2157fce9e65f79e501d41746f x86_64 xorg-x11-server-Xdmx-1.20.10-5.el8_4.x86_64.rpm SHA-256: 0e007eb3105194b05adb862e7ee55616d0d4ecb64e3437a0b92feb9a85fe8426 xorg-x11-server-Xdmx-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: 640711409d9d57d3dfd4364298b2496c0efc99db65f63141dc5184640466fbda xorg-x11-server-Xephyr-1.20.10-5.el8_4.x86_64.rpm SHA-256: 2955a2270f74253738171ec6a3974156999f0356906e6d078c4f7a495f471bcd xorg-x11-server-Xephyr-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: f443dc7e77b812f7c5f7102e9fdcfaba3eaee1dfe05b2df8400cddb65388979f xorg-x11-server-Xnest-1.20.10-5.el8_4.x86_64.rpm SHA-256: 6910c78dd4d15ed54b1cb56116d56d3fc8ae27520241bc833df5099d8c61e762 xorg-x11-server-Xnest-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: cb166840d4350b37b53a27a19ef8321db4f73e43024b23b7c80f1c5f43c0ef9d xorg-x11-server-Xorg-1.20.10-5.el8_4.x86_64.rpm SHA-256: b3c7cb2207d806b48cf982c9a07030147fc7951854f1bb5e61b63466dd4c9212 xorg-x11-server-Xorg-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: 2375f3e13c8725556ba6c65c74b982a7079b65e41ec6448b3298a87ff062e72b xorg-x11-server-Xvfb-1.20.10-5.el8_4.x86_64.rpm SHA-256: 6c037c872323341912bfbc7f1720b46e06c4d85c6238c43321a41e425c96d886 xorg-x11-server-Xvfb-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: cf3095758ef5de87cf8eedae1c9439ac8aa7cfbda270c3ba7597291fad1a7494 xorg-x11-server-Xwayland-1.20.10-5.el8_4.x86_64.rpm SHA-256: c10532f545ef577711902a5c67f89d67096ab812dab689d35e2d26432d7e738b xorg-x11-server-Xwayland-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: d884619e2ea6898f829ad15761b15ef103c7e06d840590ad97d9a3fd76b229a0 xorg-x11-server-common-1.20.10-5.el8_4.x86_64.rpm SHA-256: da474f457b72ff0635c0727f472493c4b0fdac7abe4a702c4a12ccaa29f7016c xorg-x11-server-debuginfo-1.20.10-5.el8_4.x86_64.rpm SHA-256: 05a1ffd781bde0b96cb8a697f811ee19395a592ebccffbfb3903321f991f2316 xorg-x11-server-debugsource-1.20.10-5.el8_4.x86_64.rpm SHA-256: be6307d2d73233477be2406c5034f8912d856ac9f993603d07e0caba855424cb The Red Hat security contact is secalert@redhat.com . 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