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Dell ThinOS 10 CVE-2026-82157

| EUVDEUVD-2026-86394 HIGH
Improper Certificate Validation (CWE-295)
2026-09-24 dell GHSA-hxc4-7759-8jq5
8.3
CVSS 3.1 · Vendor: dell
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Attack ChainAIDerived

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

  1. Access
    Gain adjacent-network position (same VLAN/subnet)
  2. Delivery
    Intercept client TLS connection (ARP/DNS spoof)
  3. Exploit
    Present forged certificate accepted due to improper validation
  4. Execution
    Establish machine-in-the-middle session
  5. Impact
    Bypass protection mechanism and gain unauthorized access to data

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A07:2025 - Authentication Failures
ASVS 5.0
V12 - Secure Communication Certificate validation
Exploitation Conditions

Requires the attacker to hold an adjacent-network position (AV:A) - same Layer-2 broadcast domain / VLAN or Wi-Fi segment as the Dell ThinOS 10 client - from which to intercept and machine-in-the-middle a TLS connection whose server certificate the client fails to properly validate (CWE-295). No authentication (PR:N) and no user interaction (UI:N) are needed, but exploitation is bounded by network adjacency: an attacker on a routed/remote network cannot reach it, and network segmentation that isolates thin clients from untrusted hosts sharply reduces exposure. Affected configurations are Dell ThinOS 10 endpoints running a SecurityAddon build prior to 2605.10.2766_T10.

Impact

This is a genuine elevated-priority issue but not an emergency. The CVSS 3.1 base score of 8.3 (High) is driven by an adjacent-network attack vector (AV:A), low complexity (AC:L), no privileges (PR:N), no user interaction (UI:N), and high confidentiality/integrity impact (C:H/I:H) with low availability impact (A:L). The single most important limiting signal is AV:A - the attacker must be on the same logical adjacent network (same L2 segment / broadcast domain or otherwise able to intercept traffic), which materially constrains reach versus a routable AV:N flaw. No EPSS score, no CISA KEV listing, and no public exploit code were provided, so there is no evidence of active exploitation or automated weaponization; the classic MITM certificate-validation weakness is well understood conceptually but no PoC is confirmed here. Signals are internally consistent (Dell's vector matches the CWE-295 improper-certificate-validation description of a protection-mechanism bypass), so there is no CVSS-vs-description conflict to flag. Net: prioritize patching for fleets where thin clients share untrusted or shared L2 segments, but the adjacency requirement and absence of KEV/EPSS/PoC signals make widespread opportunistic exploitation unlikely.

Exploit ScenarioDerived

An attacker positioned on the same adjacent network segment as a Dell ThinOS 10 thin client (for example a rogue device or compromised host on the same VLAN/Wi-Fi) intercepts a TLS connection the client makes to a broker or backend service. Because the client improperly validates the server certificate, the attacker presents a forged or mismatched certificate that is accepted, enabling a machine-in-the-middle that bypasses the intended protection mechanism and grants unauthorized access to the session data. No public exploit code is identified at time of analysis, and no authentication or user interaction is required.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 24, 2026

Improper TLS certificate validation in Dell ThinOS 10 endpoints running SecurityAddon builds prior to 2605.10.2766_T10 lets an adjacent-network attacker bypass a protection mechanism and gain unauthorized access to client communications and credentials. The flaw is rated CVSS 8.3 (AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L), meaning no authentication or user interaction is required, but the attacker must already sit on the same Layer-2 segment, VLAN, or Wi-Fi network as the thin client to position themselves for a machine-in-the-middle interception. No public exploit code has been identified at time of analysis and the issue is not listed in CISA KEV, so this is a genuine elevated-priority issue rather than an emergency - the practical risk is driven by how flat and trusted the thin-client network segment is.

RemediationAI

The primary fix is to update Dell ThinOS 10 SecurityAddon to version 2605.10.2766_T10 or later - vendor-released patch - following the instructions in Dell advisory DSA-2026-404 at https://www.dell.com/support/kbdoc/en-us/000506503/dsa-2026-404-security-update-for-dell-thinos-10-for-multiple-vulnerabilities, typically by pushing the SecurityAddon package through Wyse Management Suite or Dell's update mechanism and then confirming the reported addon version on each endpoint after reboot. Until every device is confirmed patched, apply compensating controls that directly address the adjacent-network precondition: place thin clients on a dedicated management VLAN that is isolated from general user, guest, and IoT segments, and enforce switch-port and WLAN controls such as 802.1X, port security, DHCP snooping and dynamic ARP inspection to make host impersonation on that segment far harder - the trade-off is reduced flexibility for hot-desking, guest access and flat-network roaming, and administrative overhead in maintaining ACLs. If any thin-client network cannot be segmented, restrict it to trusted endpoints only and monitor for rogue DHCP/ARP or unexpected TLS endpoints, accepting that residual MITM risk remains until the addon is patched. Because the flaw is a client-side trust failure, server-side certificate hardening alone does not fully mitigate it.

Affected VersionsENISA

ThinOS 10 0 <SecurityAddon_2605.10.2766_T10

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Technical ContextAI · show details

The root cause is CWE-295, Improper Certificate Validation, in the Dell ThinOS 10 SecurityAddon component. ThinOS clients are stateless thin-client endpoints that depend heavily on TLS to protect management traffic (Wyse Management Suite enrollment, firmware/package downloads), authentication, and session data when connecting to VDI brokers and servers. When the client fails to correctly validate the server certificate presented during the TLS handshake - for example by accepting an untrusted, self-signed, expired, or hostname-mismatched certificate, or by not properly anchoring trust to the intended CA - an attacker positioned in the same broadcast domain can spoof the server, terminate the TLS session with their own certificate, and relay or manipulate traffic. The CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L vector confirms the assessment: adjacency-limited but low-complexity, unauthenticated and interaction-free, with high confidentiality and integrity impact (intercepted credentials, injected or modified payloads) and limited availability impact. The CPE cpe:2.3:a:dell:thinos_10:*:*:*:*:*:*:*:* confirms that all ThinOS 10 builds below the fixed SecurityAddon baseline are treated as affected, and the Dell-published advisory DSA-2026-404 (KBDOC 000506503) is the authoritative source covering this and other ThinOS 10 issues.

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Severity by source

Vendor (dell) PRIMARY 8.3 HIGH
AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
vuln.today AI 8.3 HIGH

Adjacent MITM position needed so AV:A; no auth/interaction (PR:N/UI:N); improper cert validation yields full read/tamper of the session (C:H/I:H) with only minor disruption (A:L).

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

Primary rating from Vendor (dell).

CVSS VectorVendor: dell

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

DescriptionCVE.org

Dell ThinOS 10, versions prior to SecurityAddon_2605.10.2766_T10, contains an Improper Certificate Validation vulnerability. An unauthenticated attacker with adjacent network access could potentially exploit this vulnerability, leading to Protection mechanism bypass and Unauthorized access.

Executive ViewAI

Why It Matters

Dell ThinOS 10 thin clients configured with SecurityAddon builds prior to 2605.10.2766_T10 can be tricked into trusting a fraudulent TLS endpoint, allowing an attacker positioned on the same network segment to intercept and alter communications and capture user credentials. Because thin clients commonly carry clinical, financial, or operational workflows and credentials on flat, trusted internal networks, a single compromised segment could expose many users at once. With no vendor patch yet identified and no known exploitation to date, leadership should treat this as a priority hardening and segmentation initiative rather than an emergency response.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: segment thin-client traffic onto dedicated VLANs with strict inter-VLAN and peer-to-peer controls; enforce 802.1X/NAC and switch port security with unused ports disabled; enable DHCP snooping and dynamic ARP inspection; monitor for ARP spoofing and TLS interception on affected segments; restrict what credentials and services thin clients may use; rotate credentials for exposed endpoints.

Threat Intelligence Overview

EPSS Score
0.1%
Top 98% exploitable
Prevalence
Medium
Dell ThinOS powers Wyse/enterprise thin clients common in VDI, not everywhere
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 0.1%
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
Controlled
Automatable
No
Human Impact
High
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

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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