CVE-2026-65816 — CVSS 10.0 CRITICAL Severity | NVD Vulnerability Record

Executive Summary

The CVE‑2026‑65816 vulnerability in Azure Arc permits an unauthenticated network attacker to resolve an incorrect name or reference, resulting in full privilege escalation across the Azure Arc environment. All Azure Arc deployments, regardless of region, are exposed to a CVSS 10.0 risk that can compromise confidential data, integrity of cloud‑managed resources, and availability of critical services. Immediate executive action is required to approve emergency mitigation steps, assess patch readiness, and initiate incident response planning.

Verified Facts

• Vulnerability identifier CVE‑2026‑65816 – NVD record. — Article
• Improperly‑resolved name or reference in Azure Arc enables unauthorized privilege escalation over a network. — Article
• CVSS score 10.0 with vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. — Article
• Associated CWE‑706 (Improper Use of Reserved Names). — Article

Threat Classification

Privilege‑escalation exploit targeting Azure Arc cloud‑management services; affects cloud‑service providers and enterprises using Azure Arc globally; exploitation status is currently theoretical with no public PoC disclosed (MEDIUM CONFIDENCE); attacker motivation is to gain unrestricted access to managed resources (MEDIUM CONFIDENCE).

Threat Severity Assessment

• Exploitability: Network‑remote, no authentication required (HIGH CONFIDENCE).
• Impact Scope: Complete confidentiality, integrity, and availability compromise (HIGH CONFIDENCE).
• Prevalence: Azure Arc is widely adopted across sectors (MEDIUM CONFIDENCE).
• CVSS rating of 10.0 confirms maximum severity (HIGH CONFIDENCE).

Business Impact

Successful exploitation can lead to full control of Azure‑managed workloads, exposing regulated data and triggering GDPR fines up to €20 million or 4 % of annual turnover, NIS2 penalties, and DORA compliance breaches. Operational disruption may include forced service outages for remediation, incurring estimated incident response costs of $250 K–$1 M per affected tenant. Reputational damage is amplified by public disclosure of Azure‑Arc compromise, potentially eroding customer trust and market share.

Technical Analysis

• Attack Vector: Network‑based, remote (AV:N).
• Exploitation Chain: Attacker sends a crafted request that triggers Azure Arc’s name resolution logic; the service resolves to an attacker‑controlled reference, granting elevated privileges.
• Affected Component: Azure Arc name‑resolution module (specific version not disclosed).
• Root Cause: CWE‑706 – improper handling of reserved or special names leading to privilege escalation.
• Authentication Requirement: None (PR:N).
• User Interaction: None (UI:N).
• Impact Metrics: Confidentiality, Integrity, Availability all rated High (C:H/I:H/A:H).

CVE Analysis

• CVE‑2026‑65816 — Azure Arc name‑resolution flaw — CWE‑706 — Network (AV:N) — No authentication required (PR:N) — Patch status: not yet released (as of article publication).

MITRE ATT&CK Mapping

• Privilege Escalation → T1068: Exploitation for Privilege Escalation — the vulnerability allows an attacker to gain higher privileges by exploiting Azure Arc’s name‑resolution logic.

IOC Intelligence

No public IOCs confirmed at time of publication.

Behavioral hunting indicators to implement:

• Successful Azure Arc API calls that create or modify resource references without prior authentication.
• Audit log entries showing privilege‑elevation actions originating from unknown IP ranges.
• Anomalous spikes in Azure Arc “ResolveName” operations correlated with subsequent privileged actions.
• Cross‑tenant resource access attempts that bypass standard Azure AD conditional access policies.

Detection Engineering Guidance

• Collect Azure Activity logs (resourceId, operationName, status, callerIpAddress) and Azure AD sign‑in logs.
• Correlate any “Microsoft.AzureArc/resolveName” operation with a subsequent “Microsoft.Authorization/roleAssignments/write” event within a 5‑minute window.
• Flag events where callerIpAddress is not in the organization’s trusted network range and status = “Success”.
• In SIEM, create a rule that aggregates these events and generates an alert with severity “Critical”.
• Deploy Sysmon configuration to capture process creation of “azarc.exe” (if present) with command‑line arguments containing “--resolve”.

Sigma Rules

title: Azure Arc Privilege Escalation via Name Resolution
id: 3f9c2a1e-5b7d-4f9a-8c3e-1d2b6e7f9a0b
status: experimental
description: Detects a successful Azure Arc name‑resolution operation followed by a role assignment change, indicative of CVE‑2026‑65816 exploitation.
author: CYBERDUDEBIVASH Sentinel Apex
logsource:
    product: azure
    service: activitylog
detection:
    selection_resolve:
        operationName|contains: "ResolveName"
        status: "Success"
    selection_role:
        operationName|contains: "roleAssignments/write"
        status: "Success"
    timeframe: 5m
    condition: selection_resolve and selection_role
falsepositives:
    - Legitimate automated provisioning scripts
level: critical
tags:
    - attack.t1068

Threat Hunting Queries

• Hypothesis: Unauthenticated Azure Arc name resolution followed by privilege change — AzureActivity | where operationName contains "ResolveName" and status == "Success" and callerIpAddress !in (trustedIPs) | join kind=inner (AzureActivity | where operationName contains "roleAssignments/write" and status == "Success") on $left.resourceId == $right.resourceId and $right.timeGenerated - $left.timeGenerated <= 5m.
• Hypothesis: Role assignments created from unknown service principals — AzureActivity | where operationName == "Microsoft.Authorization/roleAssignments/write" and callerIdentity !contains "ManagedIdentity" and callerIpAddress !in (trustedIPs).
• Hypothesis: Spike in ResolveName API calls — AzureMetrics | where metricName == "ResolveNameCount" and TimeGenerated > ago(1h) and Total > 100.
• Hypothesis: Cross‑tenant resource access without Azure AD token — AzureADSignInLogs | where resultType == 0 and authenticationDetails == "" and resourceId contains "Microsoft.AzureArc".
• Hypothesis: Unexpected process execution of Azure Arc binaries — Sysmon | where EventID == 1 and Image endswith "azarc.exe" and CommandLine contains "--resolve".

SOC Analyst Playbook

• P0 – Immediate (0‑1 hr): Query Azure Activity logs for any “ResolveName” successes from non‑trusted IPs; if found, isolate the affected Azure Arc resource and block the source IP.
• P1 – Urgent (1‑4 hr): Review role‑assignment changes linked to the same resource; revert unauthorized assignments and force re‑authentication for all Azure AD accounts with access to Azure Arc.
• P2 – Same‑day (4‑24 hr): Generate a full audit report, engage Microsoft support for mitigation guidance, and begin evidence preservation for potential incident response.

Executive Decision Matrix

Executive Recommendations

• Day 1‑7: Enforce strict network ACLs to block all inbound Azure Arc name‑resolution requests from external sources; deploy the Sigma rule and SIEM alerts immediately.
• Day 8‑30: Conduct a comprehensive Azure Arc inventory, apply least‑privilege role assignments, and work with Microsoft to test any available mitigation scripts.
• Day 31‑90: Integrate Azure Arc vulnerability monitoring into the organization’s continuous compliance framework, and formalize a patch‑management SLA for cloud‑service components.

MSSP Opportunities

• Prioritize notification to clients with Azure Arc workloads, emphasizing the immediate need for network ACL hardening.

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