Red Hat Product Errata RHSA-2026:26709 - Security Advisory Issued: 2026-06-17 Updated: 2026-06-17 RHSA-2026:26709 - Security Advisory Overview Updated Packages Synopsis Important: xorg-x11-server security, bug fix, and enhancement 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. 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) Bug Fix(es) and Enhancement(s): [xserver] Backport other security fixes without a CVE assigned [rhel-8.10.z] (JIRA:RHEL-184289) 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 8 x86_64 Red Hat Enterprise Linux for IBM z Systems 8 s390x Red Hat Enterprise Linux for Power, little endian 8 ppc64le Red Hat Enterprise Linux for ARM 64 8 aarch64 Red Hat CodeReady Linux Builder for x86_64 8 x86_64 Red Hat CodeReady Linux Builder for Power, little endian 8 ppc64le Red Hat CodeReady Linux Builder for ARM 64 8 aarch64 Red Hat CodeReady Linux Builder for IBM z Systems 8 s390x Red Hat Enterprise Linux for x86_64 - Extended Life Cycle 8.10 x86_64 Red Hat Enterprise Linux for ARM 64 - Extended Life Cycle 8.10 aarch64 Red Hat Enterprise Linux for Power, little endian - Extended Life Cycle 8.10 ppc64le Red Hat Enterprise Linux for IBM z Systems - Extended Life Cycle 8.10 s390x 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 8 SRPM xorg-x11-server-1.20.11-28.el8_10.2.src.rpm SHA-256: 49e2c2fba89ff19cdc6624ccbb17d0e58162a1549e6fef09c64981b5501be63d x86_64 xorg-x11-server-Xdmx-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: 0f414866bc46f4a366b691ddd79234575bba0d931386b25c79a9fe1479d17ac9 xorg-x11-server-Xdmx-debuginfo-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: b46b9990bd7fb4db4ab48f48e2f194a1f0d663d198cd9aa35417648655995e1f xorg-x11-server-Xephyr-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: 16a37d59176c18f05c98592f0390419d6d07299adbbd62d43875f686cec0ca04 xorg-x11-server-Xephyr-debuginfo-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: 396fd7668c1ced4ebe0d43b7cc330c9334f81b01da5a8db86f9fd5cdfd30439d xorg-x11-server-Xnest-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: 8932ab88f98d6332e86270b2bf0204e6b1b050d044ed42548c499f546f175b8f xorg-x11-server-Xnest-debuginfo-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: eda36b52cd0715410694a28f02b4fcd90d3240a947f00a821173d9df76beb695 xorg-x11-server-Xorg-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: 27809e6e7433b05f38a92d8fa6f0576bfbb88f00571643d4482f85b24b2bf17f xorg-x11-server-Xorg-debuginfo-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: 7496a12513e671c1c27a3b989b5b827e78898d9b134f68ef9797e6cb5a412ffd xorg-x11-server-Xvfb-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: 12d6ec7317f3cccf3cebab4cee8857cb94f14b74b9f76073cee88eb4f67c8b93 xorg-x11-server-Xvfb-debuginfo-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: bdba85c88b48934640a79af9ab94d431d911da3d33bfe41ed845d3cb104947c0 xorg-x11-server-common-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: 268258c62b0d95502cd1fd8a82918ce8f7945dcb9467da2f8a456aa215da43ae xorg-x11-server-debuginfo-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: f71b8527bce733738d808d3f27e19e754ebe42a5f1bf5aa4909d61f7e77a3714 xorg-x11-server-debugsource-1.20.11-28.el8_10.2.x86_64.rpm SHA-256: 5031754530a7d7cee2ecb40872ea4608cb0ea2494caa40c2ac237a834499fcdb Red Hat Enterprise Linux for IBM z Systems 8 SRPM xorg-x11-server-1.20.11-28.el8_10.2.src.rpm SHA-256: 49e2c2fba89ff19cdc6624ccbb17d0e58162a1549e6fef09c64981b5501be63d s390x xorg-x11-server-Xdmx-1.20.11-28.el8_10.2.s390x.rpm SHA-256: 74f7b9276d9579950b0efa66073d2411a7b550fb9a935c6cd6b78a7ecd317681 xorg-x11-server-Xdmx-debuginfo-1.20.11-28.el8_10.2.s390x.rpm SHA-256: 7adcdab3606046f46236eb083487c65a9e47e8aa4bc631a98806d8ce7ef9eed1 xorg-x11-server-Xephyr-1.20.11-28.el8_10.2.s390x.rpm SHA-256: 286a58dbe26951c8e50762afcee8aa9fa3bb3c425a75972428a709a5c5fab1b0 xorg-x11-server-Xephyr-debuginfo-1.20.11-28.el8_10.2.s390x.rpm SHA-256: e84427c5b050fb90146af5e4183797153267666cbe3a62bdc1ffca3b6e91b94f xorg-x11-server-Xnest-1.20.11-28.el8_10.2.s390x.rpm SHA-256: d58770d8f1fbc7a05a87a8521b36b855970ee51126bf19b19d5e34ec6d7dd7d9 xorg-x11-server-Xnest-debuginfo-1.20.11-28.el8_10.2.s390x.rpm SHA-256: 961b8b86f66cb915e659cf4d37a04cbb6249bf7a451dbb1095d311023272dd75 xorg-x11-server-Xorg-1.20.11-28.el8_10.2.s390x.rpm SHA-256: 56aa9efff8fed274dfc1b439615248b9907f391b0ab20e6f24352d93434d3802 xorg-x11-server-Xorg-debuginfo-1.20.11-28.el8_10.2.s390x.rpm SHA-256: c5dd893b326a48f2b2fbbc2bb97753ca9e0478fcf5efe4de867ef4b71b8bb6bc xorg-x11-server-Xvfb-1.20.11-28.el8_10.2.s390x.rpm SHA-256: 5b832c2e3fb41c5502d56b5b48d81d271e8903146679aceee30f6808f7d89f58 xorg-x11-server-Xvfb-debuginfo-1.20.11-28.el8_10.2.s390x.rpm SHA-256: 58dd0c68ca0da333a81de2d90e8e1ddf97b0118fc60f5c5028840d5d0ac753e7 xorg-x11-server-common-1.20.11-28.el8_10.2.s390x.rpm SHA-256: 12eeca93e3c40ef7dc5959b203d694bf974c823fe6d9c6aa764c1c979f36285f xorg-x11-server-debuginfo-1.20.11-28.el8_10.2.s390x.rpm SHA-256: 55db0599579fa767c976f3181928b5c06acab5dca8db575eec2c58a9d0adee06 xorg-x11-server-debugsource-1.20.11-28.el8_10.2.s390x.rpm SHA-256: ab956b38e62b540ddd46c471be5a8ed2c424db73141ebaa083b65d7e29152779 Red Hat Enterprise Linux for Power, little endian 8 SRPM xorg-x11-server-1.20.11-28.el8_10.2.src.rpm SHA-256: 49e2c2fba89ff19cdc6624ccbb17d0e58162a1549e6fef09c64981b5501be63d ppc64le xorg-x11-server-Xdmx-1.20.11-28.el8_10.2.ppc64le.rpm SHA-256: 02be0a84b6b24b2f194b0ef784f514c7c6a76c5dbc25076bbd3587cc70ce535f xorg-x11-server-Xdmx-debuginfo-1.20.11-28.el8_10.2.ppc64le.rpm SHA-256: e5f3adf196ae9a7fd6b6200bc27bfb3f4e75219b38c0c393e547453e44d25601 xorg-x11-server-Xephyr-1.20.11-28.el8_10.2.ppc64le.rpm SHA-256: 5e90d04382a09ca4fe290e20cfefb56ccfec37caadfde4b8317feb1d8734ad9f xorg-x11-server-Xephyr-debuginfo-1.20.11-28.el8_10.2.ppc64le.rpm SHA-256: cb7f8328074286a83d79e707586323627cbc99ad491c1b701f8f0dbe94d06a95 xorg-x11-server-Xnest-1.20.11-28.el8_10.2.ppc64le.rpm SHA-256: 9c5e57981c052ad2eb8a407f4512ef26c8dd72f7a5f237cefc48cb1a85cd7f55 xorg-x11-server-Xnest-debuginfo-1.20.11-28.el8_10.2.ppc64le.rpm SHA-256: 2949a7fd07c86ef8061ae9b3e3f50dfb2c908c0a656826325c206522fa96d8a4 xorg-x11-server-Xorg-1.20.11-28.el8_10.2.ppc64le.rpm SHA-256: 4162d33e75c06b31139967bbad360b0ec5f163f4727af978d45a41e813fef012 xorg-x11-server-Xorg-debuginfo-1.20.11-28.el8_10.2.ppc64le.rpm SHA-256: e1adb5661cb081cb51ebb345a7923