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

State: Published
Severity: 7.8 High
Published: Jun 5, 2026
Updated: Sep 28, 2026
Reserved: Jun 4, 2026

Read the record on cve.org

Description

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 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.

Scores

CVSS	Score	Vector	Source
3.1	7.8 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	redhat
3.1	7.8 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	redhat-SADP

Weaknesses

CWE-121 Stack-based Buffer Overflow

Affected Products

Product	Versions
Red Hat Enterprise Linux 10Red Hat	0:24.1.9-4.el10_2.2 and laterNot affected
Red Hat Enterprise Linux 10.0 Extended Update SupportRed Hat	0:24.1.5-6.el10_0.1 and laterNot affected
Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSIONRed Hat	0:1.1.0-25.el6_10.18 and laterNot affected
Red Hat Enterprise Linux 7 Extended Lifecycle SupportRed Hat	0:1.20.4-35.el7_9 and laterNot affected
Red Hat Enterprise Linux 7 Extended Lifecycle SupportRed Hat	0:1.8.0-36.el7_9.5 and laterNot affected
Red Hat Enterprise Linux 8Red Hat	0:21.1.3-20.el8_10.2 and laterNot affected
Red Hat Enterprise Linux 8Red Hat	0:1.20.11-28.el8_10.2 and laterNot affected
Red Hat Enterprise Linux 8Red Hat	0:1.15.0-10.el8_10 and laterNot affected
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportRed Hat	0:1.20.10-5.el8_4 and laterNot affected
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportRed Hat	0:1.11.0-8.el8_4.16 and laterNot affected
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-OnRed Hat	0:1.20.10-5.el8_4 and laterNot affected
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-OnRed Hat	0:1.11.0-8.el8_4.16 and laterNot affected
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportRed Hat	0:1.20.11-8.el8_6 and laterNot affected
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportRed Hat	0:21.1.3-2.el8_6.7 and laterNot affected
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportRed Hat	0:1.12.0-6.el8_6.18 and laterNot affected
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-OnRed Hat	0:1.20.11-8.el8_6 and laterNot affected
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-OnRed Hat	0:21.1.3-2.el8_6.7 and laterNot affected
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-OnRed Hat	0:1.12.0-6.el8_6.18 and laterNot affected
Red Hat Enterprise Linux 8.8 Telecommunications Update ServiceRed Hat	0:1.20.11-19.el8_8 and laterNot affected
Red Hat Enterprise Linux 8.8 Telecommunications Update ServiceRed Hat	0:21.1.3-13.el8_8.1 and laterNot affected
Red Hat Enterprise Linux 8.8 Telecommunications Update ServiceRed Hat	0:1.12.0-15.el8_8.18 and laterNot affected
Red Hat Enterprise Linux 8.8 Update Services for SAP SolutionsRed Hat	0:1.20.11-19.el8_8 and laterNot affected
Red Hat Enterprise Linux 8.8 Update Services for SAP SolutionsRed Hat	0:21.1.3-13.el8_8.1 and laterNot affected
Red Hat Enterprise Linux 8.8 Update Services for SAP SolutionsRed Hat	0:1.12.0-15.el8_8.18 and laterNot affected
Red Hat Enterprise Linux 9Red Hat	0:24.1.9-4.el9_8.2 and laterNot affected
Red Hat Enterprise Linux 9Red Hat	0:1.20.11-34.el9_8.2 and laterNot affected
Red Hat Enterprise Linux 9Red Hat	0:1.15.0-7.el9_8.2 and laterNot affected
Red Hat Enterprise Linux 9.2 Update Services for SAP SolutionsRed Hat	0:1.20.11-21.el9_2 and laterNot affected
Red Hat Enterprise Linux 9.2 Update Services for SAP SolutionsRed Hat	0:21.1.3-10.el9_2.1 and laterNot affected
Red Hat Enterprise Linux 9.2 Update Services for SAP SolutionsRed Hat	0:1.12.0-14.el9_2.15 and laterNot affected
Red Hat Enterprise Linux 9.4 Update Services for SAP SolutionsRed Hat	0:1.20.11-29.el9_4 and laterNot affected
Red Hat Enterprise Linux 9.4 Update Services for SAP SolutionsRed Hat	0:22.1.9-8.el9_4.1 and laterNot affected
Red Hat Enterprise Linux 9.4 Update Services for SAP SolutionsRed Hat	0:1.13.1-8.el9_4.10 and laterNot affected
Red Hat Enterprise Linux 9.6 Extended Update SupportRed Hat	0:1.20.11-34.el9_6 and laterNot affected
Red Hat Enterprise Linux 9.6 Extended Update SupportRed Hat	0:23.2.7-6.el9_6.1 and laterNot affected
Red Hat Enterprise Linux 9.6 Extended Update SupportRed Hat	0:1.14.1-11.el9_6 and laterNot affected
Red Hat Enterprise Linux 6Red Hat

References

RHSA-2026:26562vendor-advisory
RHSA-2026:26566vendor-advisory
RHSA-2026:26590vendor-advisory
RHSA-2026:26610vendor-advisory
RHSA-2026:26709vendor-advisory
RHSA-2026:28923vendor-advisory
RHSA-2026:29844vendor-advisory
RHSA-2026:36083vendor-advisory
RHSA-2026:36085vendor-advisory
RHSA-2026:36086vendor-advisory
RHSA-2026:36087vendor-advisory
RHSA-2026:36632vendor-advisory
RHSA-2026:36633vendor-advisory
RHSA-2026:36634vendor-advisory
RHSA-2026:36768vendor-advisory
RHSA-2026:36791vendor-advisory
RHSA-2026:36792vendor-advisory
RHSA-2026:36798vendor-advisory
RHSA-2026:38502vendor-advisory
RHSA-2026:38810vendor-advisory
RHSA-2026:46377vendor-advisory
RHSA-2026:46382vendor-advisory
RHSA-2026:46385vendor-advisory
RHSA-2026:46392vendor-advisory
RHSA-2026:46456vendor-advisory
RHSA-2026:46460vendor-advisory
RHSA-2026:46473vendor-advisory
RHSA-2026:49519vendor-advisory
https://access.redhat.com/security/cve/CVE-2026-50258vdb-entry
RHBZ#2485383issue-tracking
https://gitlab.freedesktop.org/xorg/xserver/-/commit/543e108516428fc8c3bea91d6563ad266f9a801e
https://lists.x.org/archives/xorg-announce/2026-June/003702.html
https://redhat.atlassian.net/browse/PSIRTSUPT-16950
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-50258.json

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