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libX11 EUVDEUVD-2026-88175

| CVE-2026-94284 MEDIUM
Out-of-bounds Read (CWE-125)
2026-09-28 suse GHSA-5j4r-gpq7-9www
5.5
CVSS 3.1 · Vendor: suse
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Attack ChainAIDerived

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

  1. Access
    Lure client to malicious X server
  2. Exploit
    Send crafted XIM trigger-key registration data
  3. Execution
    Trigger out-of-bounds read in parser
  4. Impact
    Crash attached X client (DoS)

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, read limits
MITRE ATT&CK

1 technique across 1 tactic: Collection

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

Exploitation Conditions

Exploitation requires an X11 client built against a vulnerable libX11 (before 1.8.14) to connect to a malicious or compromised X server, and the client must use the X Input Method (XIM) path that performs trigger-key registration parsing. The limiting factors are significant: the trust model is inverted (server attacks client), so an attacker must control the X server the victim connects to (e.g., a hostile remote display, malicious SSH X-forwarding endpoint, or attacker-set DISPLAY), user interaction is needed to establish that connection (UI:R), and the vector is local (AV:L) rather than network-facing. Impact is limited to crashing the affected client application (availability only).

Impact

This is a medium-severity denial-of-service issue, not a high-priority remote code execution flaw. The provided CVSS 3.1 vector (AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H, 5.5) is internally consistent with the description: the attack vector is local (AV:L) because exploitation occurs over an X11 connection where the X client must connect to a malicious/compromised X server, user interaction is required (UI:R) for that connection to be established, and the only impact is availability (A:H, client crash) with no confidentiality or integrity loss (C:N/I:N). Notably, although CWE-125 (out-of-bounds READ) and the 'Information Disclosure' tag might suggest data leakage, the vendor-scored vector explicitly sets C:N and the description states only that clients can be crashed - so the demonstrated impact is DoS, and the 'Information Disclosure' framing is misleading. No EPSS score, no CISA KEV listing, and no public POC are present in the supplied intelligence, so exploitation status is 'no public exploit identified at time of analysis.' The inverted trust model (a malicious server attacking clients) further limits practical risk: it typically requires a user to be induced to connect a client to an attacker-controlled X server, which is uncommon in normal desktop use. Net: a real but low-urgency bug worth patching in routine cycles rather than emergency response.

Exploit ScenarioDerived

A user is induced to run an X11 client application against an attacker-controlled or compromised X server (for example via a manipulated DISPLAY, an SSH X-forwarding session to a hostile host, or a malicious remote display). During XIM trigger-key registration the malicious server returns crafted data that drives the client's parser to read out of bounds, crashing the client application. No public exploit code is identified in the provided intelligence; a vendor patch (freedesktop MR 310) is available.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 28, 2026

Crashing of X11 client applications can be triggered by a malicious X server exploiting an out-of-bounds read in libX11's X Input Method (XIM) trigger-key registration parser in versions before 1.8.14. This is a medium-severity denial-of-service issue (CVSS 5.5) that requires the victim to connect to an attacker-controlled X server, with user interaction (UI:R) and no authentication required (PR:N), but impact is limited to availability (client crash). No public exploit identified at time of analysis, and it is not confirmed actively exploited (CISA KEV).

RemediationAI

Upgrade to libX11 1.8.14 or later (Vendor-released patch: libX11 1.8.14), which contains the fix from X.Org libX11 merge request 310 (https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_requests/310/diffs?commit_id=1b7904002d212eed40949ccf4e8e7156f9fec0e2). As compensating controls, avoid connecting X11 clients to untrusted or attacker-controlled X servers (e.g., hostile remote displays, untrusted SSH X-forwarding endpoints, or attacker-set DISPLAY variables); this may limit remote GUI functionality. Another mitigation is to disable the XIM trigger-key registration path if the application does not require it, though this can degrade input method support. There is no indication that network-level blocking is applicable since the attack vector is local. Apply the patch as the primary remediation.

Affected VersionsENISA

libX11 0 <1.8.14

Affected Packages

euvd libx11 fix: 1.8.14

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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

Technical ContextAI · show details

The vulnerability is an out-of-bounds read (CWE-125) in libX11, the core X11 client library used by applications to communicate with X servers. Specifically, the flaw resides in the parser that handles trigger-key registration messages as part of the X Input Method (XIM) protocol. When an X client connects to a malicious or compromised X server, the server can send a crafted XIM message that causes the client to read beyond allocated memory, leading to a crash. The CVSS vector (AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H) indicates a local attack vector requiring user interaction, no privileges, and only availability impact. The affected CPE is cpe:2.3:a:x.org:libx11:*:*:*:*:*:*:*:* for versions prior to 1.8.14. This is an inverted trust model where the server attacks the client, and exploitation is limited to denial of service.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (suse) PRIMARY 5.5 MEDIUM
AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
vuln.today AI 5.5 MEDIUM

Local X11 connection to a malicious server (AV:L), victim must initiate the client connection (UI:R), no auth on client side (PR:N), impact limited to client crash (A:H, C:N/I:N).

3.1 AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.0 AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE MEDIUM
Red Hat 5.5 MEDIUM

Primary rating from Vendor (suse).

CVSS VectorVendor: suse

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

DescriptionCVE.org

An out-of-bounds read vulnerability in libX11's XIM trigger-key registration parser in libX11 before 1.8.14 could be used by malicious X servers to crash attached X clients.

Threat Intelligence Overview

EPSS Score
0.1%
Top 99% exploitable
Prevalence
High
libX11 is the core X11 client library on virtually all Linux/Unix desktops
Data Quality
5 sources
Confidence: Medium
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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.1%
Patch available Yes
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
Scheduled
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact· derived
High
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

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.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
Container bci/openjdk-devel:17.0.20.1-21.73 Container bci/openjdk-devel:21.0.12.1-25.73 Container bci/openjdk-devel:25.0.4.1-9.74 Container bci/openjdk:17.0.20.1-20.63 Container bci/openjdk:21.0.12.1-24.62 Container bci/openjdk:25.0.4.1-9.62 Container private-registry/1.2/harbor-portal:1.2.1-1.126 Container private-registry/harbor-portal:1.1.3-2.147 Image SLES15-SP7-Azure-Basic Affected
Container suse/kiosk/firefox-esr:153.3-75.48 Container suse/kiosk/pulseaudio:17.0-73.45 Container suse/kiosk/tigervnc-x11vnc:1.14-63.46 Container suse/kiosk/xorg-client:21-81.10 Container suse/kiosk/xorg:21.1-83.45 Affected
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise Module for Basesystem 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed

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