High severity · published Jun 5, 2026
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
7.8
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 5% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 10.0 Extended Update Support · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 6 · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSION · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 7 Extended Lifecycle Support · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 8.8 Telecommunications Update Service · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions · Red Hat
All versions, or not specified · source: vendor, CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-50258
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-50258
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:26562
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:26566
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:26590
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:26610
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:26709
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:28923
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