Skip to main content
View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain local user session on RHEL host
  2. Delivery
    Connect to running X server via DISPLAY
  3. Exploit
    Send crafted XkbSetMap request with oversized key type index
  4. Execution
    Overflow mapWidths[256] stack buffer in _XkbSetMapChecks()
  5. Persist
    Hijack saved return address in server process
  6. Impact
    Execute attacker-controlled code as root or session user

Vulnerability Assessment

Weakness
CWE
CWE-121
ASVS 5.0
V15 - Secure Coding and Architecture Stack buffer bounds checking
MITRE ATT&CK

1 technique across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Sign in to read
Exploitation Conditions

The attacker must have local access to the target system with the ability to open an authenticated connection to the running X server (a logged-in user session, an interactive console seat, or any account permitted by the xauth/MIT-MAGIC-COOKIE-1 mechanism to connect to :0). The vulnerable code path requires that the X server process the attacker's XkbSetMap request via the XKB extension, which is enabled by default on Xorg and Xwayland builds. Privilege escalation to root specifically requires that the Xorg binary is running as root - true on RHEL 6 and 7 by default and on RHEL 8+ when Xorg is launched outside a logind/rootless session; under rootless Xorg or pure Xwayland (Wayland session), exploitation is limited to code execution in the user's own session rather than root. No user interaction by another party is needed (UI:N), and no special non-default configuration beyond standard XKB support is required.
Impact

The CVSS 3.1 vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H produces a base score of 7.8 - High severity, but explicitly local with low-privilege authentication required, meaning the attacker must already have a session on the system that can connect to the X server. No EPSS score, KEV listing, or public POC was provided in the intelligence sources, so this is currently no public exploit identified at time of analysis and is not on CISA KEV. The real-world priority is moderate: in modern RHEL 8/9/10 setups using Wayland or rootless Xorg, the privilege escalation impact is bounded to the user session; however, on RHEL 6/7 and any deployment where Xorg still runs as root (multi-user servers, kiosks, legacy desktops), this becomes a credible local privilege escalation primitive. EPSS data is missing, which is typical for very recently disclosed flaws - defenders should treat exploit probability as undetermined rather than low.
Exploit ScenarioDerived

A local user with a valid login session (SSH, console, or kiosk account) connects to the running X server using their own DISPLAY credentials, then sends a crafted XkbSetMap request whose key type index exceeds 256, triggering the stack overflow inside _XkbSetMapChecks(). On a system where Xorg runs as root - for example a RHEL 7 multi-user workstation or a console-launched Xorg session - corruption of the saved return address allows the attacker to redirect execution and obtain a root shell; on rootless Xorg deployments the same primitive yields code execution in the X server's user context, which is still useful for escaping restricted graphical shells or kiosks. No public POC has been published at time of analysis, but the bug pattern (fixed-size stack array indexed by an attacker-controlled value) is straightforward to weaponize once the patch diff is examined.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.0% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAIv1 – Jun 05, 2026

Stack-based buffer overflow in X.Org X server and Xwayland's _XkbSetMapChecks() function allows local authenticated attackers to crash the server or potentially escalate privileges to root when the X server runs with elevated privileges. The flaw resides in CheckKeyTypes() writing to a fixed mapWidths[256] stack buffer at a client-controlled offset, affecting Red Hat Enterprise Linux versions 6 through 10. No public exploit identified at time of analysis, but an upstream fix has been merged into the xserver repository.

RemediationAI

Upstream fix available (commit 867b59b33bee669cb412f1314e47c52eacf6e00b in gitlab.freedesktop.org/xorg/xserver); released patched version not independently confirmed from the provided references - administrators should monitor the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-50259 and apply the xorg-x11-server and xwayland errata packages once published via yum/dnf update for their RHEL major version. As a compensating control until patched packages are installed, run Xorg rootless where supported (RHEL 8+ defaults) so that a successful overflow yields user-level rather than root-level code execution, accepting the trade-off that some legacy input drivers and VT switching features may require additional configuration. On RHEL 6/7 systems where root-mode Xorg is still default, restrict local interactive logins to trusted users only and consider migrating console-only servers off of running the X server entirely; on RHEL 9/10 deployments, prefer Wayland sessions where Xwayland still requires patching but reduces the attack surface available to remote X clients. The freedesktop announcement at https://lists.x.org/archives/xorg-announce/2026-June/003702.html should be consulted for the exact upstream tag containing the fix.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Sign in to check
Technical ContextAI · show details

X.Org X server is the reference implementation of the X11 display server protocol, and Xwayland is its compatibility layer for running X11 clients under Wayland compositors. The vulnerability is a classic CWE-121 stack-based buffer overflow in the XKB (X Keyboard Extension) handling code: _XkbSetMapChecks() allocates a fixed 256-element mapWidths array on the stack, then CheckKeyTypes() writes into this array using an index supplied by the client without bounds validation. Because XKB requests are processed by the server on behalf of any connected X client, a malicious local client can craft an XkbSetMap request with an out-of-range key type index, corrupting stack memory in the server process. On distributions where the X server still runs as root (common on legacy RHEL deployments and headless/console setups), corruption of saved return addresses or function pointers can yield root-level code execution.

Know when Red Hat Enterprise Linux 10 gets its next vulnerability

  • Watch products and get an email when something new is published
  • Check this CVE against your own stack and servers
  • Exploit and PoC references, threat intelligence from 22 sources
Continue with Google Continue with GitHub

No credit card · 7-day full trial

Severity by source

Vendor (redhat) PRIMARY 7.8 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SUSE HIGH
Red Hat 7.8 HIGH

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionCVE.org

A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. _XkbSetMapChecks() declares a fixed-size stack buffer mapWidths[256] indexed by key type index. The helper function CheckKeyTypes() writes to this buffer at a client-controlled offset, allowing a stack buffer overflow. This may be used to crash the server, or for privilege escalation if the X server runs as root.

Zero Day Initiative Advisories

ZDI-26-393 X.Org Server SetMap Request Stack-based Buffer Overflow Privilege Escalation Vulnerability Jun 2026

Executive ViewAI

Why It Matters

X.Org X server and Xwayland contain a stack buffer overflow affecting Red Hat Enterprise Linux 6 through 10 that allows authenticated local users to escalate privileges to root; no public exploit identified at time of analysis. No vendor-released patch identified at time of analysis. Organizations running these services should immediately restrict local user access to affected systems and monitor for future patch availability.

Business Impact: High
Compensating Controls

Restrict local shell access to systems running X server; run X11/Xwayland services with minimum necessary privileges (not root); disable X services entirely if not operationally required; implement host-level access controls and monitor local account creation.

Threat Intelligence Overview

EPSS Score
0.0%
Top 98% exploitable
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment MSRC Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.0%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact
High
Technical Impact
Total

Priority Score

39
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +39
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Privilege Escalation HIGH

Privilege escalation occurs when an attacker leverages flaws in access control mechanisms to gain permissions beyond what they were originally granted.

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Stack-based Buffer Overflow HIGH

A stack-based buffer overflow occurs when a program writes more data to a buffer located on the stack than it was allocated to hold.

Affected Products (CPE)CVE.org

cpe:2.3:a:red_hat:red_hat_enterprise_linux_10:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_6:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_7:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_8:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_8:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_9:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_9:*:*:*:*:*:*:*:*

More in Red Hat Enterprise Linux 10

View all
CVE-2026-18663 MEDIUM
5.9 Aug 12

Heap corruption via double-free in 389-ds-base's LDAP control parsing allows an unauthenticated remote attacker to crash
CVE-2026-4631 CRITICAL POC
9.8 Apr 07

Remote code execution in Cockpit's web interface allows unauthenticated attackers to execute arbitrary commands on the h
CVE-2026-4480 CRITICAL POC
9.0 May 26

Remote code execution in Samba's printing subsystem allows remote attackers to inject arbitrary shell commands via craft
CVE-2026-101258 HIGH POC
7.8 Oct 06

Ghostscript can execute arbitrary shell commands with the privileges of its process when it renders a crafted PostScript
CVE-2026-96889 HIGH POC
7.8 Sep 23

Use-after-free in librsvg during rendering of crafted SVG documents with nested XInclude directives and duplicate entity
CVE-2026-4775 HIGH POC
7.8 Mar 24

A signed integer overflow vulnerability exists in the libtiff library's putcontig8bitYCbCr44tile function that leads to

CVE-2026-114406 MEDIUM POC
6.8 Oct 21

The system CA trust store shipped in Red Hat's ca-certificates RPM packages includes eMudhra root authorities that signe
CVE-2026-18922 CRITICAL
9.8 Sep 07

Authentication bypass in 389 Directory Server (shipped as Red Hat Directory Server 11-13 and within RHEL 6-10) lets remo
CVE-2026-14544 CRITICAL
9.8 Jul 03

Remote code execution and privilege escalation in HPLIP (HP Linux Imaging and Printing) affects the hpcups print filter

CVE-2026-76578 CRITICAL
9.8 Sep 07

Unauthenticated privilege escalation in FreeIPA (Red Hat Identity Management) allows a remote attacker to gain genuine a
CVE-2026-102560 CRITICAL
9.8 Sep 29

A heap buffer overflow exists in libsoup's WebSocket permessage-deflate compression path: when a very large outbound mes
CVE-2026-5121 HIGH
7.5 Mar 30

Remote code execution in libarchive on 32-bit systems allows unauthenticated attackers to execute arbitrary code via spe

Same weakness CWE-121 – Stack-based Buffer Overflow

View all
CVE-2025-0282 CRITICAL POC
9.0
CVE-2025-22457 CRITICAL POC
9.8
CVE-2012-10060 CRITICAL POC
9.3
CVE-2012-10053 CRITICAL POC
9.3
CVE-2013-10064 CRITICAL POC
9.3
CVE-2012-10023 MEDIUM POC
6.9
CVE-2012-10058 CRITICAL POC
10.0
CVE-2013-10068 CRITICAL POC
9.4

Same technique Privilege Escalation

View all
CVE-2024-0012 CRITICAL POC
9.3
CVE-2025-47812 CRITICAL POC
10.0
CVE-2013-0422 CRITICAL POC
9.8
CVE-2013-0632 CRITICAL POC
9.8
CVE-2024-9474 MEDIUM POC
6.9
CVE-2017-5689 CRITICAL POC
9.8
CVE-2021-20021 CRITICAL POC
9.8
CVE-2017-12635 CRITICAL POC
9.8

Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Module for Basesystem 15 SP7 Affected
SUSE Linux Enterprise Module for Development Tools 15 SP7 Affected

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-50259 ADVISORY https://vuldb.com/vuln/368894 REF https://access.redhat.com/errata/RHSA-2026:26562 REF https://access.redhat.com/errata/RHSA-2026:26566 REF https://access.redhat.com/errata/RHSA-2026:26590 REF https://access.redhat.com/errata/RHSA-2026:26610 REF https://access.redhat.com/errata/RHSA-2026:26709 REF https://access.redhat.com/errata/RHSA-2026:28923 REF https://access.redhat.com/errata/RHSA-2026:29844 REF https://access.redhat.com/errata/RHSA-2026:36083 REF https://access.redhat.com/errata/RHSA-2026:36085 REF https://access.redhat.com/errata/RHSA-2026:36086 REF https://access.redhat.com/errata/RHSA-2026:36087 REF https://access.redhat.com/errata/RHSA-2026:36632 REF https://access.redhat.com/errata/RHSA-2026:36633 REF https://access.redhat.com/errata/RHSA-2026:36634 REF https://access.redhat.com/errata/RHSA-2026:36768 REF https://access.redhat.com/errata/RHSA-2026:36791 REF https://access.redhat.com/errata/RHSA-2026:36792 REF https://access.redhat.com/errata/RHSA-2026:36798 REF https://access.redhat.com/errata/RHSA-2026:38502 REF https://access.redhat.com/errata/RHSA-2026:38810 REF https://access.redhat.com/errata/RHSA-2026:46377 REF https://access.redhat.com/errata/RHSA-2026:46382 REF https://access.redhat.com/errata/RHSA-2026:46385 REF https://access.redhat.com/errata/RHSA-2026:46392 REF https://access.redhat.com/errata/RHSA-2026:46456 REF https://access.redhat.com/errata/RHSA-2026:46460 REF https://access.redhat.com/errata/RHSA-2026:46473 REF https://access.redhat.com/errata/RHSA-2026:49519 REF https://access.redhat.com/security/cve/CVE-2026-50259 REF https://bugzilla.redhat.com/show_bug.cgi?id=2485384 REF https://gitlab.freedesktop.org/xorg/xserver/-/commit/867b59b33bee669cb412f1314e47c52eacf6e00b REF https://lists.x.org/archives/xorg-announce/2026-June/003702.html REF https://redhat.atlassian.net/browse/PSIRTSUPT-16950 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-50259.json

Search Externally

GitHub PoC Exploit-DB PacketStorm Snyk Rapid7 Nuclei Templates Trickest PoC
Back

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy