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libX11 EUVDEUVD-2026-88174

| CVE-2026-94283 MEDIUM
Out-of-bounds Read (CWE-125)
2026-09-28 suse GHSA-j5qx-6vm4-vfcj
6.5
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 attribute response
  3. Execution
    Trigger out-of-bounds read in libX11 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 the victim's X11 client (linked against libX11 before 1.8.14) to connect to a malicious or compromised X server, which then returns crafted XIM (X Input Method) attribute data parsed by the vulnerable attribute parser. The limiting factor is this inverted trust relationship: clients normally connect only to a trusted local or forwarded display, so an attacker must control the X server the client attaches to (e.g., a hostile remote display, a compromised X11-forwarding endpoint, or a spoofed DISPLAY). Impact is limited to crashing the client (availability), with no code execution or data disclosure demonstrated.

Impact

The provided CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H, base 6.5) is internally consistent with the description: impact is availability-only (client crash / denial of service), with no confidentiality or integrity impact despite the CWE-125 out-of-bounds READ classification. The 'reverse' threat model is the key nuance - this is not a client attacking a server, but a malicious or compromised X server attacking the X clients that attach to it, which is why UI:R is present (a client must connect to the hostile server). No EPSS score, no CISA KEV entry, and no public POC were supplied, so exploitation status is 'no public exploit identified at time of analysis.' A patch is confirmed available (freedesktop GitLab MR 310, commit 42d0303f). Net assessment: this is a moderate, DoS-only issue whose real-world risk is bounded by the unusual precondition (trusting a malicious X server) and the availability-only impact. It is not a high-priority, mass-exploitable flaw; it warrants routine patching via distro updates rather than emergency response. Note the input tags 'Information Disclosure' and 'Buffer Overflow' overstate impact - the confirmed effect is a crash, not data disclosure or memory corruption/write.

Exploit ScenarioDerived

A user connects an X11 client (e.g., via SSH X11 forwarding or to a remote/attacker-controlled display) to a malicious X server. The server returns crafted XIM (X Input Method) attribute data that the client's libX11 attribute parser reads out of bounds, crashing the client application. No public exploit code was identified, and the impact is limited to denial of service (application crash).

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 28, 2026

Remote, unauthenticated attackers who control an X server can crash X clients linked against libX11 before 1.8.14 by returning crafted XIM (X Input Method) attribute data, because the parser performs an out-of-bounds read (CWE-125). This is an availability-only denial-of-service (CVSS 6.5, AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H) limited by an inverted trust relationship: the victim's client must attach to the attacker's display, so exploitation requires the user to connect to a malicious, compromised, or spoofed X server. No public exploit code has been identified at time of analysis, and the issue is not listed in CISA KEV.

RemediationAI

Upgrade to libX11 1.8.14 or later; the upstream fix is available as a merge request (commit 42d0303f243002a9856c76060569a61893c670dd) at https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_requests/310/diffs?commit_id=42d0303f243002a9856c76060569a61893c670dd. If immediate upgrade is not possible, restrict X11 clients to trusted local or authenticated SSH-forwarded displays, avoid setting DISPLAY to untrusted hosts, and prevent X11 forwarding to remote endpoints that are not fully trusted. Monitor for repeated client crashes in XIM-enabled applications as a potential indicator of a hostile X server. Disabling XIM support or input methods can remove the attack surface but will break input for non-Latin scripts and complex text entry, so it is a temporary workaround rather than a long-term fix.

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

libX11 is the reference client-side implementation of the X11 protocol. XIM (X Input Method) lets clients negotiate input methods with an X server, exchanging attribute lists that the client parses to configure locale and input handling. CVE-2026-94283 is an out-of-bounds read (CWE-125) in that attribute parser: a malicious X server returns malformed XIM attribute data that causes the client to read beyond the intended buffer, leading to a crash (denial of service) on the client. The CPE cpe:2.3:a:x.org:libx11:*:*:*:*:*:*:*:* covers all libX11 versions before the fix. Although tags include 'Information Disclosure' and 'Buffer Overflow', the authoritative assessment finds no demonstrated data disclosure or code execution; the practical impact is availability loss on the attached client. The patch is an upstream merge request (commit 42d0303f243002a9856c76060569a61893c670dd) at https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_requests/310/diffs?commit_id=42d0303f243002a9856c76060569a61893c670dd.

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Severity by source

Vendor (suse) PRIMARY 6.5 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
vuln.today AI 6.5 MEDIUM

Malicious X server reaches clients over the network (AV:N) and the client must actively connect to it (UI:R); out-of-bounds read causes a crash only, so C:N/I:N/A:H.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE MEDIUM
Red Hat 6.5 MEDIUM

Primary rating from Vendor (suse).

CVSS VectorVendor: suse

Attack Vector
Network
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 (X Input Method) attribute parser in libX11 before 1.8.14 could be used by malicious X servers to crash attached X clients.

Threat Intelligence Overview

EPSS Score
0.2%
Top 91% exploitable
Prevalence
High
core X11 client library present on virtually all Linux/Unix desktop systems
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 0.2%
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
Open
Automatable
No
Human Impact· derived
High
Technical Impact
Partial

Priority Score

32
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +32
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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