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Windows DHCP Server EUVDEUVD-2026-73490

| CVE-2026-69405 MEDIUM
Memory Leak (CWE-401)
2026-09-08 secure@microsoft.com GHSA-rcpq-5hxq-5829
5.7
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 authenticated adjacent-network access
  2. Delivery
    Send crafted DHCP requests to trigger leak path
  3. Exploit
    Repeat to progressively exhaust server heap
  4. Execution
    DHCP Server process runs out of allocatable memory
  5. Impact
    DHCP service fails, denying IP assignment to network clients

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Resource cleanup, leak prevention
Exploitation Conditions

The attacker must be present on the same network segment as the Windows DHCP Server (AV:A - same subnet, VLAN, or adjacent broadcast domain; not exploitable from the internet). Low-privilege authorization is required (PR:L - the description explicitly states 'authorized attacker', ruling out fully anonymous exploitation). No user interaction is required. The Windows Server DHCP Server role must be installed and active. Exploitation is limited to availability impact; confidentiality and integrity of DHCP data are not affected. Factors limiting risk include: adjacency boundary (cannot traverse routers without relay configuration), authentication requirement, and the absence of any confirmed public exploit or active exploitation.

Impact

The CVSS base score of 5.7 (Medium) accurately reflects the constrained threat model: AV:A limits attacker reach to the local network segment, and PR:L (authorized attacker per the description) requires some level of network authentication or credential. The impact is confined to availability (A:H) with C:N and I:N, so data exfiltration or configuration tampering are not in scope. No CISA KEV listing and no POC are noted, reducing urgency relative to a critical, remotely exploitable flaw. Real-world risk is highest in environments where the DHCP Server role is exposed to untrusted authenticated users on the same VLAN - a common scenario in shared enterprise or campus networks. The vulnerability is not automatable without adjacency, limiting mass-exploitation potential. EPSS data was not supplied; the bounded attack vector and authentication requirement suggest low-to-moderate exploitation probability.

Exploit ScenarioDerived

An authenticated user on the same subnet as a vulnerable Windows DHCP Server sends a high volume of crafted DHCP requests designed to trigger the allocation path that omits memory deallocation. Over time the DHCP Server process's working set grows until the host's available memory is exhausted, causing the DHCP service to stop responding and denying IP assignment to all legitimate network clients on that segment. No public proof-of-concept tooling for this specific vulnerability is known at time of analysis.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.6% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 09, 2026

Memory exhaustion in Windows DHCP Server enables an authorized attacker on the adjacent network to crash or degrade the DHCP service via repeated triggering of a CWE-401 memory leak. The vulnerability affects the Windows Server DHCP Server role across Windows Server 2012 through 2025, including Server Core installations. Exploitation requires low-privilege adjacency and results exclusively in availability loss - no confidentiality or integrity impact. No public exploit identified at time of analysis; vendor patch is available.

RemediationAI

Apply the Microsoft security updates that bring affected builds to or above the fixed build numbers confirmed by EUVD: Windows Server 2025 to 10.0.26100.33438, Windows Server 2022 to 10.0.20348.5622, Windows Server 2019/Windows 10 1809 to 10.0.17763.9245, Windows Server 2016/Windows 10 1607 to 10.0.14393.9512, Windows Server 2012 R2 to 6.3.9600.23397, and Windows Server 2012 to 6.2.9200.26349. Details are available at the MSRC advisory https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69405. Where immediate patching is not possible, a compensating control is to restrict VLAN-level access to the DHCP Server so that only trusted management hosts or authenticated workstation segments can reach UDP ports 67-68; note this may complicate DHCP relay scenarios. Restarting the DHCP Server service can temporarily recover memory without a full server reboot, but does not remediate the underlying leak.

Affected VersionsENISA

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

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

CWE-401 (Missing Release of Memory After Effective Lifetime) describes a condition where memory allocated during DHCP request processing is never subsequently freed. The Windows DHCP Server is a Microsoft-native server role providing automatic IP address assignment via the DHCP protocol (UDP/67-68). Because the memory is not released after the allocation's effective lifetime expires, an attacker who can generate sufficient DHCP traffic can progressively exhaust the DHCP Server process's heap, eventually causing service failure. The CVSS vector AV:A confirms the exploit path is bounded to the adjacent network (same subnet or VLAN), not the global internet.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 5.7 MEDIUM
AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
vuln.today AI 5.7 MEDIUM

Adjacent network access and low-privilege authorization required per description; impact is availability-only memory exhaustion with no confidentiality or integrity effect.

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

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

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

Lifecycle Timeline

2
Patch available
Sep 08, 2026 - 18:35 EUVD
CVE Published
Sep 08, 2026 - 18:19 cve.org
MEDIUM 5.7

DescriptionCVE.org

Missing release of memory after effective lifetime in Windows DHCP Server allows an authorized attacker to deny service over an adjacent network.

Threat Intelligence Overview

EPSS Score
0.6%
Top 55% exploitable
Prevalence
High
Windows Server DHCP role widely deployed in enterprise networks
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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.6%
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
Scheduled
Exploitation
None
System Exposure· derived
Controlled
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

29
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +28
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0
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