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AD CS EUVDEUVD-2026-73569

| CVE-2026-69821 HIGH
Improper Encoding or Escaping of Output (CWE-116)
2026-09-08 secure@microsoft.com GHSA-3m3q-63xj-gjcr
7.8
CVSS 3.1 · Vendor: microsoft
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Attack ChainAIDerived

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

  1. Access
    Obtain low-privileged domain credentials
  2. Delivery
    Authenticate locally or via RDP to AD CS server
  3. Exploit
    Submit crafted certificate request with malformed output-triggering input
  4. Execution
    Trigger improper encoding flaw in AD CS output processing
  5. Persist
    Execute arbitrary code as SYSTEM
  6. Impact
    Issue rogue domain certificates or persist via CA compromise

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Output encoding for downstream
Exploitation Conditions

The attacker must have an authenticated low-privileged session on the affected host - specifically a machine running the Active Directory Certificate Services role. Authentication is confirmed by the CVSS PR:L metric. The AD CS role must be installed and running (it is not present in default Windows installations; it requires explicit server role deployment). No network exposure is required; the exploit is executed locally. Limiting factors: exploitation is constrained to systems where AD CS is installed; standard Windows workstations and servers without the certificate services role are not affected. The attack is further limited to users who can log on locally or via remote desktop to the AD CS server, which in hardened environments should be restricted to PKI administrators only.

Impact

The CVSS 7.8 score is well-calibrated: AV:L requires the attacker to already have local code execution, PR:L confirms a low-privileged authenticated account is sufficient, and the C:H/I:H/A:H triad reflects a complete local privilege escalation to SYSTEM or equivalent. No KEV listing and no confirmed POC reduce urgency compared to network-exploitable vulnerabilities, but AC:L and PR:L together mean that any authenticated user on an AD CS host can likely exploit this without sophisticated tooling. AD CS servers are high-value targets - they underpin PKI trust for entire domains - so post-compromise impact extends well beyond the individual server. EPSS data is absent from the provided intelligence, leaving exploitation probability unquantified. The 'Information Disclosure' tag in the input metadata is a mislabel; the CVSS C:H/I:H/A:H and the description's 'elevate privileges' language confirm this is a privilege escalation, not solely an information disclosure.

Exploit ScenarioDerived

An attacker who has obtained a low-privileged domain user account (e.g., via phishing or credential stuffing) logs on locally or via RDP to a Windows Server running AD CS. By submitting a crafted certificate request or interacting with the AD CS management interface with specially constructed output-triggering input, the attacker exploits the improper encoding flaw to break out of the normal execution context and execute code as SYSTEM, gaining full control of the PKI server and the ability to issue rogue certificates for the domain. No public POC has been confirmed at time of analysis.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 09, 2026

Local privilege escalation in Active Directory Certificate Services (AD CS) on Windows enables an authenticated low-privileged user to gain full system control (C:H/I:H/A:H) without user interaction. The root cause is CWE-116 - improper encoding or escaping of output - within the AD CS component, which Microsoft has patched across a broad range of Windows 10 and Windows Server releases from 2012 through 2025. No public exploit code or CISA KEV listing has been identified at time of analysis, but the low attack complexity (AC:L) makes this straightforward to exploit once an attacker has local access.

RemediationAI

Apply the Microsoft security update corresponding to the affected Windows build via Windows Update or WSUS; the vendor has confirmed a patch is available (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69821). Target build thresholds per platform are: Windows Server 2025 >= 10.0.26100.33438, Windows Server 2022 >= 10.0.20348.5622, Windows Server 2019/Windows 10 1809 >= 10.0.17763.9245, Windows Server 2016/Windows 10 1607 >= 10.0.14393.9512, Windows Server 2012 R2 >= 6.3.9600.23397, Windows Server 2012 >= 6.2.9200.26349. As a compensating control prior to patching, restrict interactive logon and network logon rights on AD CS servers to PKI administrators only via Group Policy (User Rights Assignment), reducing the pool of accounts able to trigger the vulnerability. Additionally, enable Advanced Audit Policy logging for certificate service events (Event IDs 4898-4899) to detect anomalous enrollment activity. Note that Windows Server 2012 and 2012 R2 have reached end of support; organizations should prioritize migration to supported versions in addition to applying this update.

Affected VersionsENISA

Windows 10 Version 1809 10.0.17763.0 <10.0.17763.9245
Windows 10 Version 1607 10.0.14393.0 <10.0.14393.9512
Windows Server 2012 R2 (Server Core installation) 6.3.9600.0 <6.3.9600.23397
Windows Server 2025 10.0.26100.0 <10.0.26100.33438
Windows Server 2012 R2 6.3.9600.0 <6.3.9600.23397
Windows Server 2012 6.2.9200.0 <6.2.9200.26349
Windows Server 2022 10.0.20348.0 <10.0.20348.5622
Windows Server 2012 (Server Core installation) 6.2.9200.0 <6.2.9200.26349
Windows Server 2016 10.0.14393.0 <10.0.14393.9512
Windows Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.33438
Windows Server 2016 (Server Core installation) 10.0.14393.0 <10.0.14393.9512
Windows Server 2019 (Server Core installation) 10.0.17763.0 <10.0.17763.9245
Windows Server 2019 10.0.17763.0 <10.0.17763.9245

Affected Packages

euvd windows_10_version_1607 fix: 10.0.14393.9512
euvd windows_10_version_1809 fix: 10.0.17763.9245
euvd windows_server_2012 fix: 6.2.9200.26349
euvd windows_server_2012_r2 fix: 6.3.9600.23397
euvd windows_server_2012_r2_server_core_installation fix: 6.3.9600.23397
euvd windows_server_2012_server_core_installation fix: 6.2.9200.26349
euvd windows_server_2016 fix: 10.0.14393.9512
euvd windows_server_2016_server_core_installation fix: 10.0.14393.9512
euvd windows_server_2019 fix: 10.0.17763.9245
euvd windows_server_2019_server_core_installation fix: 10.0.17763.9245
euvd windows_server_2022 fix: 10.0.20348.5622
euvd windows_server_2025 fix: 10.0.26100.33438
euvd windows_server_2025_server_core_installation fix: 10.0.26100.33438

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 13 packages in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Active Directory Certificate Services is Microsoft's PKI role deployed on Windows Server to issue, manage, and revoke X.509 certificates. CWE-116 (Improper Encoding or Escaping of Output) describes a class of vulnerability where data passed to a downstream interpreter - command shell, file system path, template engine, or similar - is not correctly sanitized, allowing an attacker to inject control sequences or escape intended boundaries. In the AD CS context, this likely manifests in the certificate enrollment pipeline or management interfaces where attacker-controlled input (e.g., certificate subject fields, request parameters) is processed without adequate output encoding, enabling privilege escalation on the local system. The vulnerability affects both full and Server Core installations across Windows 10 1607/1809 and Windows Server 2012 through 2025.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 7.8 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 7.8 HIGH

Local attack vector with low privileges required confirmed by 'authorized attacker elevates privileges locally'; no user interaction; full C/I/A on the compromised host.

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

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

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

Lifecycle Timeline

2
Patch available
Sep 08, 2026 - 18:35 EUVD
CVE Published
Sep 08, 2026 - 18:19 nvd
HIGH 7.8

DescriptionCVE.org

Improper encoding or escaping of output in Active Directory Certificate Services (AD CS) allows an authorized attacker to elevate privileges locally.

Executive ViewAI

Why It Matters

A privilege escalation flaw in Microsoft Active Directory Certificate Services (AD CS) affecting Windows 10 and Windows Server 2012-2025 allows any authenticated low-privileged user to gain full administrative control without requiring user interaction. This creates immediate risk to organizations' identity infrastructure and certificate-based authentication systems, since AD CS compromise can enable attackers to forge certificates and escalate across domain-joined systems.

Business Impact: High
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.3%
Top 77% exploitable
Prevalence
High
AD CS widely deployed in enterprise Windows Active Directory environments
Vendor Status
Publicly Disclosed:No
Exploited:No
Latest Software Release:Exploitation Unlikely
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 HIGH
CISA KEV No
Public POC No
EPSS 0.3%
Patch available Yes
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
High
Technical Impact
Total

Priority Score

39
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +39
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0
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