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Yamaha LAN Monitor CVE-2026-103665

| EUVDEUVD-2026-112752 HIGH
Uncontrolled Search Path Element (CWE-427)
2026-10-29 jpcert GHSA-wx4r-57mg-fmh2
8.4
CVSS 4.0 · Vendor: jpcert
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Attack ChainAIDerived

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

  1. Access
    Plant crafted DLL in installer's directory
  2. Exploit
    Administrator launches Yamaha LAN Monitor installer
  3. Execution
    Installer insecurely loads malicious DLL
  4. Impact
    Arbitrary code execution with admin privileges

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A08:2025 - Software or Data Integrity Failures
ASVS 5.0
V13 - Configuration Search path element control
Exploitation Conditions

Requires local access to write a specially crafted DLL into the directory from which the Yamaha LAN Monitor for Windows installer is executed, plus an administrator actually launching that installer from the attacker-controlled directory (UI:A). Exploitation is limited by these factors: it is local only (AV:L, not remotely reachable), depends on user interaction by a privileged user, and requires the victim to run the installer co-located with the planted DLL (commonly achieved via a crafted download bundle or a writable shared/Downloads directory). Affects installer versions up to and including Ver.1.9.3.

Impact

Signals are moderate and mostly inferred rather than confirmed. The CVSS 4.0 vector (AV:L/AC:L/AT:N/PR:N/UI:A) describes a local, user-interaction-dependent DLL search-order hijack, not a remotely-reachable flaw, so the 8.4 base score is driven by the HIGH triad impact (VC:H/VI:H/VA:H = arbitrary code execution with administrative privileges) rather than by ease of remote reach. No EPSS score, no CISA KEV entry, and no public exploit reference are present in the input, so there is no public exploit identified at time of analysis and no evidence of active exploitation. The vuln.today decision label is this_week, consistent with a serious-but-not-emergency, locally-triggered code-execution bug. Net: this is a real, patch-worthy issue for environments running the affected installer, but the AV:L and UI:A requirements make it meaningfully lower real-world risk than a comparable network-reachable RCE; it is not a drop-everything emergency absent exploitation evidence.

Exploit ScenarioDerived

An attacker plants a specially crafted DLL (using a name the installer resolves via insecure search order) into a directory such as the user's Downloads folder, then relies on an administrator downloading and launching the Yamaha LAN Monitor installer from that same directory. When the installer runs, it loads the malicious DLL and executes the attacker's code with administrative privileges. No public proof-of-concept is referenced in the available data; exploitation requires local file placement and an administrator running the installer (AV:L, UI:A).

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv2 – Oct 29, 2026

Arbitrary code execution in the Yamaha LAN Monitor for Windows installer versions up to and including Ver.1.9.3 stems from insecure DLL loading (CWE-427). A local attacker who can place a crafted DLL in the directory from which an administrator launches the installer can have that DLL loaded with the installer's administrative privileges, but the attack requires local write access and an administrator actually running the installer from that location. No CISA KEV entry or public exploit code was identified at time of analysis; the issue is local and depends on user interaction.

Earlier versions of this analysis (1)
v1 Oct 29, 2026 - 12:08 CVSS 7.8

The Windows installer for Yamaha LAN Monitor resolves DLL dependencies from the directory it is launched from, so a crafted DLL placed alongside the installer can be loaded and executed with the administrative privileges the installer runs under. The weakness is CWE-427 (uncontrolled search path element) with a vendor/NVD CVSS 3.0 base score of 7.8; the assessed vector is local (AV:L) with no privileges required (PR:N) but mandatory user interaction (UI:R), so a victim must launch the installer from a directory the attacker can write to. No public exploit has been identified at time of analysis, and there is no CISA KEV entry indicating active exploitation.

RemediationAI

The supplied sources do not state a fixed version, so consult the Yamaha and JVN advisories at https://www.rtpro.yamaha.co.jp/RT/FAQ/Security/JVN23695234.html and https://jvn.jp/en/jp/JVN23695234/ for the current patched installer release before deployment. Until a fixed installer is confirmed, restrict write access to the directory containing the installer and avoid launching it from Downloads, shared, or other user-writable locations; place the installer in a protected directory and verify its vendor signature or hash before execution. These controls reduce the DLL-planting precondition but do not remove the underlying insecure DLL search behavior, and they depend on administrator discipline and a trusted distribution path.

Affected VersionsENISA

Yamaha LAN Monitor for Windows 0 ≤Ver.1.9.3

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Technical ContextAI · show details

The flaw is an uncontrolled search path element (CWE-427) in the Windows installer for Yamaha LAN Monitor. Windows DLL search order can cause an installer to resolve a required library from its current working directory or another location writable by the attacker before a trusted system path; because the installer runs with elevated privileges, a malicious DLL placed alongside it can execute arbitrary code in that administrative context. The provided CPE identifies yamaha_corporation:yamaha_lan_monitor_for_windows, and EUVD lists versions from 0 through Ver.1.9.3 as affected; the supplied sources do not describe the precise DLL name or search path involved. The CVSS vector reflects local access, low attack complexity, no privileges, and user interaction, not remote exploitation.

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Severity by source

Vendor (jpcert) PRIMARY 8.4 HIGH
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
vuln.today AI 7.8 HIGH

Local DLL hijack needing a victim to launch the installer gives AV:L/UI:R/PR:N/AC:L; code runs with admin rights so C:H/I:H/A:H with no scope change.

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

Primary rating from Vendor (jpcert).

CVSS VectorVendor: jpcert

Attack Vector
Local
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
Active
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
High
Vulnerable system: Availability
High
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

Lifecycle Timeline

3
Analysis Updated
Oct 29, 2026 - 12:29 vuln.today
v2 - CVSS changed
CVSS changed
Oct 29, 2026 - 12:22 NVD
7.8 (HIGH) 8.4 (HIGH)
CVE Published
Oct 29, 2026 - 11:33 cve.org
HIGH 7.8

DescriptionCVE.org

The installer for Yamaha LAN Monitor for Windows provided by Yamaha Corporation may insecurely load Dynamic Link Libraries (DLLs). When the installer is launched in a directory containing a specially crafted DLL file, the malicious DLL may be loaded, resulting in arbitrary code execution with administrative privileges.

Executive ViewAI

Why It Matters

Yamaha LAN Monitor for Windows (versions up to and including 1.9.3) contains an insecure DLL loading vulnerability that could allow a local attacker to execute arbitrary code with administrative privileges if the installer is run from a directory where the attacker can place files. This means a malicious insider or attacker with local write access to the installation directory could compromise systems during software installation, potentially leading to unauthorized access or data breaches. Leadership should care because this affects the integrity of endpoint administration and requires user interaction, making it a targeted risk for organizations running this software.

Business Impact: Medium
Compensating Controls

No vendor-released patch identified at time of analysis. Limit local write access to directories containing the installer to trusted administrators; enforce application whitelisting to prevent unauthorized DLL loading; require administrators to run installers from secure, write-protected locations; and monitor for anomalous files in installer directories.

Threat Intelligence Overview

EPSS Score
0.2%
Top 91% exploitable
Prevalence
Low
niche vendor network-device management tool, limited to Yamaha equipment sites
Data Quality
4 sources
Confidence: Medium

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 0.2%
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
Defer
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact
Medium
Technical Impact
Total

Priority Score

42
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +42
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

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