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Attack ChainAIDerived

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

  1. Access
    Gain low-privilege local shell access
  2. Delivery
    Open X client connection to running X server
  3. Exploit
    Manipulate window attributes via X11 protocol
  4. Execution
    Force screen saver activation via XActivateScreenSaver
  5. Persist
    Trigger use-after-free read in CreateSaverWindow()
  6. Impact
    Receive leaked heap memory contents

Vulnerability Assessment

Weakness
CWE
CWE-416
ASVS 5.0
V15 - Secure Coding and Architecture Memory lifecycle management
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Privilege Escalation

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

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Exploitation Conditions

Exploitation requires a local account on the target system with the ability to open an X client connection to the running X server (AV:L/PR:L from CVSS vector). The specific triggering sequence is: (1) a connected X client changes window attributes on a window, and (2) forces screen saver activation - both are standard X11 protocol operations available to any authenticated X client. No special configuration or elevated privilege beyond a normal desktop user session is required. Exploitation is limited by the requirement for physical or remote shell access to the host and an active X server session; headless servers, container environments, or Wayland-only deployments without Xwayland may not be exposed. Authentication requirements are confirmed as low-privilege local access per the CVSS PR:L vector.
Impact

The CVSS 3.1 vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N places this at Medium severity (5.5). Attack Vector Local and Privileges Required Low are the dominant risk limiters: exploitation requires an established session on the target system with at least a low-privileged account and the ability to open an X client connection. Attack Complexity Low indicates no race condition or special timing is required beyond the described attribute-manipulation sequence. The Confidentiality impact is High with no Integrity or Availability impact, meaning this is a targeted data-leakage primitive rather than a code execution or denial-of-service vector. EPSS data was not provided in the input, so exploitation probability cannot be quantified from that source. The vulnerability is not in CISA KEV and no public POC is known, reducing urgency for emergency patching. Real-world priority is moderate: environments where untrusted local users share X server sessions (multi-user Linux desktops, shared development workstations) carry higher exposure than server deployments without graphical sessions.
Exploit ScenarioDerived

A low-privileged local user with shell access on a system running an X server opens an X client connection, programmatically alters window attributes on a targeted window, then issues a command to force screen saver activation. This sequence causes CreateSaverWindow() to read from a freed heap region, and the server returns or leaks the stale memory contents to the client - potentially including sensitive data resident in the X server's heap at the time of the free. No public POC exists at time of analysis, but the attack complexity is rated Low, suggesting the steps are straightforward once the trigger sequence is understood.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Jun 05, 2026

Use-after-free read in X.Org X server and Xwayland's CreateSaverWindow() function exposes heap memory to local authenticated users, resulting in information disclosure. A low-privileged local X client can manipulate window attributes and force screen saver activation to trigger a read from freed memory, leaking potentially sensitive heap contents (C:H/I:N/A:N). No public exploit identified at time of analysis, and this vulnerability is not listed in CISA KEV; however, an upstream fix commit has been published and a Red Hat advisory is available.

RemediationAI

The primary fix is the upstream commit ecc634f1b2f7aa473d3a267eada98c4918bf9e05 to the xorg/xserver repository on freedesktop.org GitLab; a tagged release version incorporating this fix is not independently confirmed from the provided data, so administrators should monitor the xorg-announce mailing list post at https://lists.x.org/archives/xorg-announce/2026-June/003702.html for an official release announcement. Red Hat users should apply updated xorg-x11-server and xwayland packages once they are published via Red Hat Errata - track the advisory at https://access.redhat.com/security/cve/CVE-2026-50263. As a compensating control, restricting X server access to trusted local users only (e.g., via xhost restrictions or mandatory access controls such as SELinux) reduces the attack surface by limiting which processes can open X client connections; note that this does not eliminate the flaw but raises the privilege bar for exploitation. Disabling the screen saver entirely (e.g., via xset s off) may prevent the triggering condition but has not been confirmed as a complete mitigation by the vendor and could have usability side effects.

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Technical ContextAI · show details

The X.Org X server implements the X11 display protocol, with Xwayland serving as an X11 compatibility layer under Wayland compositors. CWE-416 (Use After Free) identifies the root cause: CreateSaverWindow(), the function responsible for creating the screen saver window resource, retains a reference to an object after it has been freed. When an X client sequence - changing window attributes followed by forcing screen saver activation - races or interacts with this lifecycle, the server performs a read on freed heap memory. Affected CPE strings (cpe:2.3:a:red_hat:red_hat_enterprise_linux_6 through _10) confirm the flaw is present across all currently supported and legacy RHEL releases, implicating both the packaged xorg-x11-server and xwayland components distributed by Red Hat. The freedesktop.org GitLab commit ecc634f1b2f7aa473d3a267eada98c4918bf9e05 represents the upstream patch to the shared xserver codebase.

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Severity by source

Vendor (redhat) PRIMARY 5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
SUSE MEDIUM
Red Hat 5.5 MEDIUM

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
None
Availability
None

DescriptionCVE.org

A use-after-free flaw was found in the X.Org X server and Xwayland in CreateSaverWindow(). A client can trigger a use-after-free read after changing window attributes and forcing the screen saver, leading to information disclosure.

Zero Day Initiative Advisories

ZDI-26-397 X.Org Server CreateSaverWindow Use-After-Free Information Disclosure Vulnerability Jun 2026

Threat Intelligence Overview

EPSS Score
0.0%
Top 98% exploitable
Social Media
1
Sightings
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment MSRC Vendor CIRCL 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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.0%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
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· derived
Defer
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

28
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +28
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Use After Free HIGH

Use-after-free vulnerabilities occur when a program continues to access memory through a pointer after that memory has been deallocated.

Memory Corruption HIGH

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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:*:*:*:*:*:*:*:*

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Same weakness CWE-416 – Use After Free

View all
CVE-2019-0708 CRITICAL POC
9.8
CVE-2015-5119 CRITICAL POC
9.8
CVE-2014-0322 HIGH POC
8.8
CVE-2012-4792 HIGH POC
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CVE-2009-4324 HIGH POC
7.8
CVE-2015-0313 CRITICAL POC
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CVE-2015-5122 CRITICAL POC
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CVE-2013-2551 HIGH POC
8.8

Same technique Information Disclosure

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CVE-2019-2725 CRITICAL POC
9.8
CVE-2021-34523 CRITICAL POC
9.0
CVE-2013-2251 CRITICAL POC
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CVE-2017-5638 CRITICAL POC
9.8
CVE-2025-24813 CRITICAL POC
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CVE-2025-68613 HIGH POC
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CVE-2015-1701 HIGH POC
7.8
CVE-2017-0147 HIGH POC
7.5

Vendor StatusVendor

SUSE

Severity: Moderate
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-2026-50263 ADVISORY https://vuldb.com/vuln/368919 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-2026-50263 REF https://bugzilla.redhat.com/show_bug.cgi?id=2485388 REF https://gitlab.freedesktop.org/xorg/xserver/-/commit/ecc634f1b2f7aa473d3a267eada98c4918bf9e05 REF https://lists.x.org/archives/xorg-announce/2026-June/003702.html REF https://redhat.atlassian.net/browse/PSIRTSUPT-16950

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