{"id":"CVE-2026-50258","title":"A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland","summary":"A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. The X server has multiple stack buffers sized XkbMaxShiftLevel * XkbNumKbdGroups but CheckKeyTypes() does not verify or clamp non-canonical key types to Xkb…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-121","CWE-121"],"vendor":"x.org","product":"x_server","affected":["x_server < 21.1.23","xwayland < 24.1.12","enterprise_linux = 7.0","enterprise_linux = 8.0","enterprise_linux = 9.0","enterprise_linux = 10.0"],"patched":["x_server 21.1.23","xwayland 24.1.12"],"published":"2026-06-05","updated":"2026-07-07","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-50258","references":[{"url":"https://access.redhat.com/errata/RHSA-2026:26562","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:26566","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:26590","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:26610","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:26709","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:28923","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:29844","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:36086","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/security/cve/CVE-2026-50258","label":"secalert@redhat.com"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2485383","label":"secalert@redhat.com"},{"url":"https://gitlab.freedesktop.org/xorg/xserver/-/commit/543e108516428fc8c3bea91d6563ad266f9a801e","label":"secalert@redhat.com"},{"url":"https://lists.x.org/archives/xorg-announce/2026-June/003702.html","label":"secalert@redhat.com"},{"url":"https://redhat.atlassian.net/browse/PSIRTSUPT-16950","label":"secalert@redhat.com"},{"url":"https://access.redhat.com/errata/RHSA-2026:26562","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:26566","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:26590","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:26610","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:26709","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:28923","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/errata/RHSA-2026:29844","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://access.redhat.com/security/cve/CVE-2026-50258","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2485383","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-50258.json","label":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"}],"tags":["nvd"],"epss":0.00161,"epssPercentile":0.05729,"ingestedAt":"2026-07-07T08:52:24.927Z","slug":"CVE-2026-50258","body":"## Overview\n\nA stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. The X server has multiple stack buffers sized XkbMaxShiftLevel * XkbNumKbdGroups but CheckKeyTypes() does not verify or clamp non-canonical key types to XkbMaxShiftLevel. A client can change key types to excessive shift levels and trigger stack overflows. This is caused by an incomplete fix of CVE-2025-26597. This may be used to crash the server, or for privilege escalation if the X server runs as root.\n\n## Affected\n\n- `x_server < 21.1.23`\n- `xwayland < 24.1.12`\n- `enterprise_linux = 7.0`\n- `enterprise_linux = 8.0`\n- `enterprise_linux = 9.0`\n- `enterprise_linux = 10.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `x_server 21.1.23`\n- `xwayland 24.1.12`","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}