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Windows Update Orchestrator EUVDEUVD-2026-100060

| CVE-2026-83933 MEDIUM
Improper Link Resolution Before File Access (CWE-59)
2026-10-13 secure@microsoft.com GHSA-vgwm-wc78-3gq8
5.5
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 local account
  2. Delivery
    Plant malicious symbolic link in watched path
  3. Exploit
    Trigger Update Orchestrator file access
  4. Execution
    Service follows link to protected file
  5. Impact
    Read disclosed file contents

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V5 - File Handling Symlink resolution safety
Exploitation Conditions

Requires the attacker to already hold a local, authenticated low-privileged account on the target Windows machine (PR:L, AV:L) and the ability to create or control filesystem links (symbolic/hard/junction) in a location the Windows Update Orchestrator Service accesses. Exploitation hinges on winning a link-resolution race against the SYSTEM service so it dereferences an attacker-controlled link to a protected file; no user interaction is needed (UI:N). Limiting factors: there is no remote vector (fully local), the attacker needs valid credentials/a foothold first, and impact is confined to information disclosure (C:H, I:N, A:N) - no code execution or modification. SSVC Automatable=no indicates it is not reliably mass-exploitable, further narrowing realistic abuse to post-compromise privilege/confidentiality escalation.

Impact

This is a genuine but comparatively low-priority vulnerability, and the available signals are consistent rather than conflicting. The provided CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N, base 5.5 MEDIUM) describes a local, low-complexity attack that requires existing low-privileged authentication and yields only confidentiality impact (information disclosure) with no integrity or availability effect. CISA's SSVC framework corroborates the low urgency: Exploitation=none (no observed or public exploitation), Automatable=no (cannot be reliably scripted at scale), and Technical Impact=partial. No EPSS score was supplied, the CVE is NOT on CISA KEV, and no public proof-of-concept is referenced - so exploitation status is 'no public exploit identified at time of analysis.' All signals therefore align toward a real-but-not-urgent issue: the local AV and required privileges sharply limit real-world risk, meaning this is a defense-in-depth / privilege-boundary bug rather than an internet-facing emergency. The main caveat is missing data (no EPSS, no POC telemetry), but absence of those signals is itself consistent with the 'Exploitation: none' SSVC determination and does not contradict the CVSS picture.

Exploit ScenarioDerived

A low-privileged authenticated user on a Windows host plants or manipulates a symbolic/hard link (CWE-59) that the SYSTEM-level Windows Update Orchestrator Service follows while accessing a file, causing the service to read a protected file and disclose its contents to the attacker. Because the CVSS vector is AV:L/PR:L, the attacker must already have local, authenticated access and win the link-resolution race; no public exploit code is identified at time of analysis.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 14, 2026

Improper link resolution in the Windows Update Orchestrator Service allows a locally authenticated, low-privileged attacker to read files they would not otherwise be permitted to access on Windows 10, Windows 11 (23H2 through 26H2) and Windows Server 2022/2025. Because the service runs as SYSTEM and dereferences filesystem paths without validating reparse points, an attacker who already holds a foothold can plant a symbolic link, junction or hard link and race the service into opening a protected file, yielding high-confidentiality information disclosure with no integrity or availability impact (CVSS 5.5). Exploitation is assessed as non-automatable under CISA's SSVC framework, no public exploit code has been identified at time of analysis, and overall risk is comparatively low-priority given the local, post-compromise prerequisites.

RemediationAI

Vendor-released patch is available: apply the Microsoft monthly cumulative update that raises each affected build to or above the fixed revisions published in the MSRC advisory (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83933) - Windows 10 21H2/22H2 to 10.0.19044.7807, Windows 11 23H2 to 10.0.22631.7652, Windows 11 24H2 to 10.0.26100.9711, Windows 11 25H2 to 10.0.26200.9711, Windows 11 26H1 to 10.0.28000.3231, Windows 11 26H2 to 10.0.26300.9711, Windows Server 2022 to 10.0.20348.5761, and Windows Server 2025 (including Server Core) to 10.0.26100.33650. Where patching must be staged, the most direct compensating control is to tighten NTFS ACLs on the directories the Update Orchestrator Service reads so that non-administrative users cannot create, rename or replace files and reparse points there; this is the more reliable measure because hard links and junctions do not require the SeCreateSymbolicLinkPrivilege that can otherwise be withheld from standard users, and removing that privilege alone leaves the attack path partially open. Additional defense-in-depth options are to audit and remove unexpected reparse points in system and servicing directories and to alert on the service opening files outside its expected paths - both are detection-oriented, add monitoring overhead, and do not remove the need to install the vendor update. No public exploit code has been identified at time of analysis and CISA SSVC records no active exploitation, so remediation can be prioritized with normal patch-cycle urgency rather than emergency response.

Affected VersionsENISA

Windows Server 2025 10.0.26100.0 <10.0.26100.33650
Windows 11 Version 25H2 10.0.26200.0 <10.0.26200.9711
Windows Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.33650
Windows Server 2022 10.0.20348.0 <10.0.20348.5761
Windows 11 Version 23H2 10.0.22631.0 <10.0.22631.7652
Windows 11 version 26H1 10.0.28000.0 <10.0.28000.3231
Windows 10 Version 21H2 10.0.19044.0 <10.0.19044.7807
Windows 10 Version 22H2 10.0.19045.0 <10.0.19044.7807
Windows 11 Version 26H2 10.0.26300.0 <10.0.26300.9711
Windows 11 Version 24H2 10.0.26100.0 <10.0.26100.9711

Affected Packages

euvd windows_10_version_21h2 fix: 10.0.19044.7807
euvd windows_10_version_22h2 fix: 10.0.19044.7807
euvd windows_11_version_23h2 fix: 10.0.22631.7652
euvd windows_11_version_24h2 fix: 10.0.26100.9711
euvd windows_11_version_25h2 fix: 10.0.26200.9711
euvd windows_11_version_26h1 fix: 10.0.28000.3231
euvd windows_11_version_26h2 fix: 10.0.26300.9711
euvd windows_server_2022 fix: 10.0.20348.5761
euvd windows_server_2025 fix: 10.0.26100.33650
euvd windows_server_2025_server_core_installation fix: 10.0.26100.33650

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 10 packages in euvd

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

Technical ContextAI · show details

The root cause is CWE-59, improper link resolution before file access (link following). The Windows Update Orchestrator Service runs under the SYSTEM account and performs file operations against update-related directories that a local low-privileged user may be able to influence. When the service resolves a path without confirming that the target is not a reparse point, an attacker able to create a symbolic link, NTFS junction or hard link in that path can redirect the SYSTEM process into opening an arbitrary protected file. Exploitation hinges on winning a race between link creation and the service's file access, which is consistent with CISA's SSVC assessment marking Automatable as 'no' and Technical Impact as 'partial'. The vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N confirms a fully local attack that requires a valid low-privileged account, requires no user interaction, leaves scope unchanged, and is confined to confidentiality with no modification or denial-of-service effect. The affected builds span the Windows 10 21H2/22H2, Windows 11 23H2/24H2/25H2/26H1/26H2 and Windows Server 2022/2025 servicing lines tracked under EUVD-2026-100060, and Microsoft attributes the report to secure@microsoft.com.

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Severity by source

Vendor (microsoft) PRIMARY 5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
vuln.today AI 5.5 MEDIUM

Local link-following requires a pre-existing low-privileged account (AV:L, PR:L); low complexity for the race, confidentiality-only impact so C:H, I:N, A:N, unchanged scope.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/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
None
Availability
None

Lifecycle Timeline

2
Patch available
Oct 13, 2026 - 20:20 EUVD
CVE Published
Oct 13, 2026 - 19:20 cve.org
MEDIUM 5.5

DescriptionCVE.org

Improper link resolution before file access ('link following') in Windows Update Orchestrator Service allows an authorized attacker to disclose information locally.

Threat Intelligence Overview

EPSS Score
0.4%
Top 65% exploitable
Prevalence
Ubiquitous
Windows Update Orchestrator Service ships in all supported Windows client and server builds
Vendor Status
Publicly Disclosed:No
Exploited:No
Latest Software Release:Exploitation Less Likely
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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.4%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
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· derived
Defer
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

28
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +28
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

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