High severity · published Apr 23, 2026
CVE-2026-33999
Xorg: xwayland: x.org x server: denial of service via integer underflow in xkb compatibility map handling
7.8
CVSS
0.4%
EPSS
No
On KEV
Description
A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violations and potentially a denial of service (DoS) or other severe impacts.
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)0.4% · higher than 32% 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 8.6 Telecommunications Update Service · Red Hat
All versions, or not specified · source: vendor, CISA
RH
Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions · Red Hat
All versions, or not specified · source: vendor, CISA
In the news
VulnerabilityHigh
ZDI-26-333: X.Org Server XkbSetCompatMap Integer Underflow Privilege Escalation Vulnerability
This vulnerability allows local attackers to escalate privileges on affected installations of X.Org Server. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The ZDI has assigned a CVSS rating of 7.8. The following CVEs are assigned: CVE-2026-33999.
Jun 9, 2026·Zero Day Initiative
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33999
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-33999
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:10739
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:11352
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:11369
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:11388
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:11656
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:11692
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