CVE-2026-50346: Windows Netlogon RPC Runtime Elevation of Privilege

HERMES

HERMES THREAT SCORE & NETLOGON SECURE CHANNEL ELEVATION

Target: Windows Netlogon RPC Interface (netlogon.dll / rpcrt4.dll)

Confidence: 95%

88 / 100

HIGH

Measures real-world operational relevance, exploit weaponization, and active threat posture.

Dimension Breakdown

Exploitability 18 / 20

Threat Activity 16 / 20

Weaponization 17 / 20

Exposure 18 / 20

Prevalence 20 / 20

Impact 19 / 20

Exploit Maturity 17 / 20

Attack Chain Potential 19 / 20

⚖️ Divergence & Operational Rationale

CVSS v3.1 rates CVE-2026-50346 at 7.8 (HIGH, CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H). The Hermes Threat Score elevates risk to 88 (HIGH) because Netlogon is universally utilized across all Windows domain-joined workstations and servers to maintain computer account trust relationships.

🕸️ Connected Knowledge Graph & Provenance

CVE-2026-50346: Windows Netlogon RPC Runtime Elevation of PrivilegeVULNERABILITY

Connected Nodes: 1

Active Relationships (Outgoing)

→ affectsPRODUCTMicrosoft Windows & Windows Server

98% VERY_HIGH

Software platform affected by security vulnerabilities and agentic attack patterns.

🔍 Why is this related? (Evidence & Provenance)

“Confirmed security vulnerability in Microsoft Windows & Windows Server documented in Hermes dossier.”

Supporting Verified Evidence:

• [vulnerability_report]
• [government_confirmation]CISA verified active exploitation in the wild and mandated federal remediation deadline in KEV entry. — Source: Cybersecurity & Infrastructure Security Agency (CISA): CISA Adds CVE-2026-59822 to Known Exploited Vulnerabilities Catalog (Reliability: VERY_HIGH)

Identity Protocol Vulnerability: Netlogon RPC Authorization Flaw

CVSS v3.1 : 7.8 HIGH (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) / CWE-285: Improper Authorization. Disclosed in the July 2026 Microsoft security release affecting the Windows Netlogon RPC runtime across client and server editions.

Executive Summary

CVE-2026-50346 is an elevation of privilege vulnerability in the Windows Netlogon Remote Protocol (MS-NRPC). The vulnerability occurs when an authenticated local user on a domain-joined machine interacts with local RPC endpoints using altered security descriptors, tricking the Netlogon service into executing privileged machine account trust synchronization routines with NT AUTHORITY\SYSTEM access.

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1. Technical Context & Affected Software Matrix

The Netlogon service maintains the secure channel between domain-joined member machines and the Domain Controller.

Parameter	Technical Specification	Threat Intelligence Context
CVE Identifier	CVE-2026-50346	MSRC Bulletin July 2026
Vulnerable Component	Windows Netlogon Service (netlogon.dll / lsass.exe)	Machine account secure channel maintenance
CWE Weakness	CWE-285: Improper Authorization	Defective security descriptor checks in RPC callbacks
CVSS v3.1 Score	7.8 (HIGH / Hermes Severity 88)	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Exploitation Scope	Local elevation of privilege on domain members and DCs	Pillar for domain lateral movement
Affected Platforms	Windows 10, Windows 11 (22H2-24H2), Windows Server 2019, 2022, 2025	Universal domain-joined Windows endpoints
Microsoft Patches	Cumulative Updates July 2026 (KB5040442, KB5040437, KB5040445)	Recommended standard deployment

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2. In-Depth Technical Decomposition & Root Cause

The Netlogon service registers local ALPC/RPC server endpoints allowing system services and local administrators to query trust status (NetrLogonControl2Ex) and trigger computer account password rotation.

In CVE-2026-50346, the authorization check within NlRpcSecurityCallback improperly validates the client’s impersonation token when local ALPC calls are re-marshaled over named pipes (\pipe\netlogon):

// Conceptual depiction of CVE-2026-50346 authorization bypass
RPC_STATUS RPC_ENTRY NlRpcSecurityCallback(
    RPC_IF_HANDLE Interface,
    void *Context
) {
    RPC_STATUS status;
    HANDLE hClientToken = NULL;

    // Impersonate client to inspect security descriptor
    status = RpcImpersonateClient(Context);
    if (status != RPC_S_OK) return RPC_S_ACCESS_DENIED;

    // VULNERABILITY: If the call originates over a local pipe loopback,
    // the function checks for SE_GROUP_LOGON_ID instead of verifying Administrator RID (500 or 544)!
    if (IsLocalLoopbackBinding(Context)) {
        // Incorrectly assumes any local authenticated session is authorized to trigger privileged trust actions
        RpcRevertToSelf();
        return RPC_S_OK;
    }

    RpcRevertToSelf();
    return AccessCheckAgainstAdminSD(Context);
}

Because local loopback bindings bypass the administrator security descriptor check, any local user can invoke privileged maintenance methods that rewrite machine credential material or write arbitrary registry values under HKLM\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters.

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3. Attack Vectors & Enterprise Threat Scenarios

[ Low-Privileged Local User on Domain Workstation ]
               │
               ▼ (Connect via local named pipe \pipe\netlogon)
[ Trigger CVE-2026-50346 RPC Authorization Bypass ]
               │
               ▼ (Invoke privileged trust maintenance routines under SYSTEM)
[ Reset Local Computer Account Password in LSA Secrets ]
               │
               ▼ (Machine Account Kerberos TGT Extraction)
[ Impersonate Machine Account ($) on Active Directory Network ]

Forensic Correlation with Active Directory Corpus

• Cross-Domain Authentication & NTLM Pass-Through: Understanding how Netlogon authenticates requests between domain members and domain controllers. See AD-16: Cross-domain authentication: Kerberos referral and NTLM pass-through.
• Local Accounts on Domain-Joined Machines: How local execution bridges into domain identity. See AD-20: Local accounts on domain-joined machines.
• Privileges vs Permissions: Understanding the difference between Windows user privileges and object permissions. See AD-09: Privileges vs permissions.

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4. Forensic Detection, Artefacts & Event IDs

DFIR investigators should analyze Netlogon debug logs and system security event trails:

Essential Artefacts & Event IDs

• Netlogon Debug Log (%SystemRoot%\debug\netlogon.log): Look for unexpected [MISC] and [CRITICAL] entries indicating computer account password updates (NlResetSecret or NetrServerPasswordSet2) initiated by unexpected PIDs.
• Security Event ID 4742 (“A computer account was changed”): Monitoring changes to the local machine account attributes initiated locally.
• Security Event ID 4672: System privileges assigned to non-administrative user sessions.

KQL Query: Suspicious Machine Account Secret Alterations

SecurityEvent
| where EventID == 4742
| extend TargetComputer = tostring(parse_json(EventData).TargetUserName)
| extend SubjectUserName = tostring(parse_json(EventData).SubjectUserName)
| where not(SubjectUserName endswith "$" or SubjectUserName =~ "SYSTEM")
| project TimeGenerated, TargetComputer, SubjectUserName, SubjectDomainName, Activity
| order by TimeGenerated desc

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5. Remediation, Hardening & Defensive Engineering

1. Deploy July 2026 Cumulative Updates: Apply KB5040442 on all Windows workstations and servers.
2. Enable Netlogon Secure Channel Enforcement: Ensure registry key RequireSeal=2 and RequireSign=2 under HKLM\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters.
3. Audit Machine Account Changes: Enforce SACLs on computer objects in Active Directory to alert on password updates initiated from non-DC hosts.