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Microsoft Azure Arc CVE-2026-69399

| EUVDEUVD-2026-82586 CRITICAL
Unintended Proxy or Intermediary ('Confused Deputy') (CWE-441)
2026-09-17 secure@microsoft.com GHSA-h8pp-hmv6-8cpq
9.9
CVSS 3.1 · NVD
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Attack ChainAIDerived

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

  1. Access
    Obtain low-privilege Azure Arc access
  2. Delivery
    Abuse confused-deputy flaw (CWE-441)
  3. Exploit
    Coerce Arc control plane to act as proxy
  4. Execution
    Cross trust boundary (scope change)
  5. Impact
    Gain elevated control of connected resources

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V4 - API and Web Service Proxy/intermediary controls
Exploitation Conditions

Exploitation requires low-privilege authenticated access to an Azure Arc context (PR:L in the vendor vector), performed remotely over the network with no user interaction (AV:N/UI:N). The specific Arc feature, API, or configuration that triggers the confused-deputy condition (CWE-441) is not described in the available sources, so the exact prerequisite setting cannot be named from the provided data. Limiting factors: an attacker must already possess some valid low-level Arc/Azure identity (it is not fully unauthenticated), and the scope change (S:C) implies the impact crosses the Arc management trust boundary into connected resources rather than staying local. No non-default configuration is documented as required, but absence of detail means this cannot be confirmed.

Impact

Signals conflict sharply and must be weighed, not averaged. Microsoft's CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H, base 9.9) describes a network-reachable, low-complexity flaw needing only low privileges, no user interaction, with a scope change and total confidentiality/integrity/availability impact - consistent with the 'Technical Impact: total' and 'Automatable: yes' entries in the SSVC record. The vuln.today decision label is 'act_now,' which aligns with that high severity and automatability. However, the real-world exploitation signals are much softer: SSVC 'Exploitation: none,' no CISA KEV listing, and no PoC or exploit reference in the provided sources, so this is NOT confirmed as actively exploited. EPSS is only 0.49% (41st percentile), i.e. low predicted 30-day exploitation probability, which contrasts with the 9.9 base score and 'act_now' label - a classic 'high-severity, not-yet-exploited' profile. The practical reading: this is a high-priority patch candidate because impact is total, the flaw is automatable, and privileges required are low, but there is currently no evidence of exploitation in the wild, so the urgency derives from potential blast radius (scope change across the Azure Arc hybrid-management trust boundary) rather than observed attacks. The description is a single stock title with no mechanism detail, so the exact trigger is not described in the available sources and the CVSS metrics should be treated as vendor-asserted, not independently reproducible.

Exploit ScenarioDerived

An attacker holding only low-privilege authenticated access within an Azure Arc-managed environment abuses a confused-deputy condition (CWE-441) to have the Arc control plane act on its behalf across a trust boundary, gaining elevated control over connected resources. Because the CVSS vector is AV:N/AC:L/PR:L/UI:N with a scope change, the action is remote, low-complexity, needs no victim interaction, and reaches resources beyond the attacker's original authorization. No public exploit has been identified at time of analysis, and the exact trigger is not described in the available sources.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 0.5% exploitation probability (EPSS)

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AnalysisAIv3 – Oct 31, 2026

Azure Arc's confused-deputy flaw (CWE-441) allows a low-privileged, authenticated remote actor to cross the service's management trust boundary and achieve high confidentiality, integrity, and availability impact across connected resources, producing a 9.9 CVSS score with Scope:Changed. Microsoft Azure Arc is affected broadly (CPE cpe:2.3:a:microsoft:azure_arc:-), and exploitation requires a valid low-level Arc/Azure identity rather than being fully unauthenticated. No public exploit has been identified at time of analysis and no CISA KEV entry is present in the provided data, with EPSS low at 0.49% (41st percentile); the vuln.today decision label is act_now because CISA SSVC rates technical impact as total and automation as feasible.

Earlier versions of this analysis (2)
v2 Sep 25, 2026 - 20:29 cvss changed CVSS 9.8

Elevation of privilege in Microsoft Azure Arc, the hybrid and multicloud control plane that projects on-premises and non-Azure servers, Kubernetes clusters and data services into Azure Resource Manager, is rated by NVD at CVSS 3.1 base 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), implying remote, low-complexity, unauthenticated attackers could reach high confidentiality, integrity and availability impact against Arc-enrolled environments. Exposure is limited to organizations that have actually onboarded resources to Arc, and the PR:N rating conflicts both with the Elevation-of-Privilege classification (which normally presumes a prior foothold) and with our internal assessment of AV:N/AC:L/PR:L/UI:N/S:C, so the unauthenticated assumption should be verified against the Microsoft update guide before it is used for risk decisions. There is no confirmed active exploitation (CVE is not in CISA KEV), no public exploit code identified at time of analysis, EPSS is low at 0.49% (41st percentile), and CISA SSVC records Exploitation: none alongside Automatable: yes and Technical Impact: total.

v1 Sep 17, 2026 - 23:31 CVSS 10.0

Elevation of privilege in Microsoft Azure Arc allows a network-reachable attacker to abuse the service as a privileged intermediary and affect resources outside the vulnerable component itself, producing full confidentiality, integrity, and availability impact across the scoped environment. The published CVSS 3.1 vector scores this 10.0 (AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H), reflecting low attack complexity, a scope change, and complete impact to the impacted resources; our independent assessment rates the same flaw with the privilege prerequisite raised to low (PR:L) and notes that the PR:N claim conflicts with typical elevation-of-privilege semantics and should be confirmed with MSRC before treating exploitation as fully unauthenticated. Only Azure Arc deployments are affected - hybrid or multicloud servers onboarded through the connected machine agent, Arc-enabled Kubernetes clusters, and Arc-enabled data services - and no public exploit code or confirmed active exploitation was identified at time of analysis.

RemediationAI

No exact fixed version is listed in the provided data; Microsoft's MSRC update guide (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69399) is the authoritative source for the patched Azure Arc build, and organizations should apply that vendor update as the complete fix. Because exploitation requires only a low-privileged Arc/Azure identity, reduce exposure in the interim by tightly restricting who can hold Arc onboarding and role-assignment permissions, reviewing existing low-privilege Arc roles for unnecessary cross-resource authority, and monitoring for unexpected scope-crossing operations; these controls lower the attack surface but do not remove the confused-deputy flaw. No specific product workaround is documented in the available sources, and the act_now priority reflects the total technical impact rather than confirmed exploitation.

Affected VersionsENISA

Azure ARC - (version not specified)

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Technical ContextAI · show details

CWE-441 (Confused Deputy) is the root-cause class: the Azure Arc control plane can act on behalf of a caller and, in this case, does not adequately bind the caller's low privilege to the authority it exercises over connected resources. The CVSS:3.1 vector AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H confirms remote, low-complexity exploitation by an authenticated low-privileged user with no user interaction, and the S:C component means the security authority changes from the Arc management context to the managed-resource context. The CPE cpe:2.3:a:microsoft:azure_arc:-:*:*:*:*:*:*:* identifies Azure Arc as the affected product but does not encode a version, and EUVD lists the affected version only as 'Azure ARC -'. The specific Arc feature, API, or configuration that triggers the confused-deputy condition is not described in the available sources.

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Severity by source

NVD PRIMARY 9.9 CRITICAL
AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
vuln.today AI 9.9 CRITICAL

Keeps vendor metrics: remote and low-complexity with low-privilege auth (PR:L, not PR:N, since some Arc identity is needed), scope change across the Arc trust boundary, total CIA impact; description too sparse to lower any metric.

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

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

5
Analysis Updated
Oct 31, 2026 - 17:28 vuln.today
v3 - CVSS changed
CVSS changed
Oct 31, 2026 - 17:22 NVD
9.8 (CRITICAL) 9.9 (CRITICAL)
Analysis Updated
Sep 25, 2026 - 20:29 vuln.today
v2 - CVSS changed
CVSS changed
Sep 25, 2026 - 20:22 NVD
10.0 (CRITICAL) 9.8 (CRITICAL)
CVE Published
Sep 17, 2026 - 23:18 nvd
CRITICAL 10.0

DescriptionNVD

Azure Arc Elevation of Privilege Vulnerability

Executive ViewAI

Why It Matters

A critical confused-deputy vulnerability in Microsoft Azure Arc allows a low-privileged, authenticated user to break the service's management trust boundary and compromise the confidentiality, integrity, and availability of connected resources across the estate. Because Azure Arc is Microsoft's control plane for managing on-premises, multicloud, and edge servers alongside native Azure resources, a successful exploitation could cascade into unauthorized control over a broad set of managed infrastructure - making this a potential enterprise-wide integrity and availability concern for any organization using Arc to govern hybrid or multicloud assets. Leadership should care because the blast radius extends beyond a single system to the management layer itself, and no vendor patch is currently available.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: enforce least privilege and credential rotation for all Arc/Azure identities; restrict network access to Arc-connected machines and agents to trusted sources; apply conditional access, MFA, and just-in-time elevation; segment Arc-managed resources to limit cross-boundary blast radius; enable centralized logging and monitoring of Arc and Azure Activity logs with alerting on anomalous cross-resource operations.

Threat Intelligence Overview

EPSS Score
0.5%
Top 59% exploitable
Prevalence
Medium
Azure hybrid/multicloud management service; significant but not universal enterprise adoption
Vendor Status
Publicly Disclosed:No
Exploited:No
Latest Software Release:N/A
Social Media
1
Sightings
Data Quality
5 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 CRITICAL
CISA KEV No
Public POC No
EPSS 0.5%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
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
Open
Automatable
Yes
Human Impact
High
Technical Impact
Total

Priority Score

50
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +50
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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