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Windows Search EUVDEUVD-2026-99436

| CVE-2026-83921 HIGH
Heap-based Buffer Overflow (CWE-122)
2026-10-13 secure@microsoft.com GHSA-p435-w46r-wh5p
7.0
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-privilege local foothold
  2. Delivery
    Craft malicious input to Search component
  3. Exploit
    Trigger heap-based buffer overflow
  4. Execution
    Execute code at SYSTEM
  5. Impact
    Full local privilege escalation

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Heap buffer bounds checking
MITRE ATT&CK

1 technique across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires the attacker to already have local, low-privileged authenticated access to the target Windows host (PR:L, AV:L) - remote or unauthenticated exploitation is not possible. The flaw resides in the Windows Search component, which is present by default across the listed Windows 10/11 and Windows Server editions, so no non-default feature toggle is indicated by the available data. The key limiting factor is HIGH attack complexity (AC:H): the attacker must satisfy specific memory-layout or timing conditions to reliably corrupt the heap, so exploitation is not guaranteed on each attempt. No user interaction is required (UI:N).

Impact

This is a genuine but moderate-priority local privilege escalation. The CVSS 3.1 vector (AV:L/AC:H/PR:L/UI:N/S:U) describes a flaw requiring local access and existing low-privilege authentication, with HIGH attack complexity - meaning exploitation depends on winning a race or satisfying memory-layout conditions that are not reliably reproducible, which materially lowers real-world weaponization likelihood. Impact is high across confidentiality, integrity, and availability (C:H/I:H/A:H), consistent with code execution at elevated privilege. Exploitation status is 'no public exploit identified at time of analysis' - this CVE is NOT in CISA KEV and no POC is referenced. No EPSS score was provided in the input, so probabilistic exploitation likelihood cannot be quantified; this is a data gap, not a low score. No SSVC decision data was supplied. The signals are internally consistent (local vector, authorized attacker, EoP classification all agree), so there is no contradiction between description and CVSS. Net: a real issue to patch in normal Patch-Tuesday cadence, not an emergency - the AC:H and PR:L constraints plus absence of exploitation evidence argue against immediate out-of-band action, though its ubiquity on Windows raises aggregate exposure.

Exploit ScenarioDerived

A low-privileged authenticated user (or malware already running in a standard user context) triggers a crafted operation against the Windows Search component to overflow a heap buffer and corrupt adjacent memory, gaining SYSTEM-level privileges. No public exploit code is identified at time of analysis, and the high attack complexity (AC:H) means the attacker must satisfy specific heap-state or timing conditions for reliable exploitation.

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 – Oct 13, 2026

Local privilege escalation in the Microsoft Windows Search component allows an attacker who already holds low-privileged authenticated access on a Windows host to corrupt the heap and elevate to a higher-integrity context. The flaw is a heap-based buffer overflow (CWE-122) reachable only locally (AV:L) with high attack complexity (AC:H), meaning the attacker must satisfy specific memory-layout conditions, and no user interaction is required (UI:N); the component ships by default across the affected Windows 10, Windows 11, and Windows Server editions, so no optional feature must be enabled. Microsoft has released vendor patches that raise the fixed OS build numbers for each affected branch, and no public exploit has been identified at time of analysis - this is a genuine but moderate-priority local privilege-escalation issue rather than a remotely exploitable or actively attacked flaw.

RemediationAI

Vendor-released patches are available: apply the Microsoft security update for CVE-2026-83921 via the MSRC update guide (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83921) or standard Windows Update / WSUS / Microsoft Update Catalog channels, bringing each host to or above its fixed build - Windows Server 2012 6.2.9200.26434, Server 2012 R2 6.3.9600.23470, Server 2016 and Windows 10 1607 10.0.14393.9612, Server 2019 and Windows 10 1809 10.0.17763.9376, Windows 10 21H2/22H2 10.0.19044.7807, Server 2022 10.0.20348.5761, Server 2025 and Windows 11 24H2 10.0.26100.33650 and 10.0.26100.9711 respectively, Windows 11 23H2 10.0.22631.7652, 25H2 10.0.26200.9711, 26H1 10.0.28000.3231, and 26H2 10.0.26300.9711; systems on end-of-servicing branches such as Windows 10 1607/1809/21H2 and Windows Server 2012/2012 R2 should be upgraded to a supported build where Extended Security Updates are not in place. Because exploitation requires pre-existing local low-privileged access, prioritise this update on multi-user endpoints, VDI/RDS session hosts, and servers where untrusted or semi-trusted users hold interactive logon rights. As a compensating control where immediate patching is not possible, restrict interactive logon and RDP access to trusted administrators, remove unnecessary local accounts, and monitor host-based telemetry for unexpected child processes or token manipulation originating from Windows Search worker processes; disabling the Windows Search service (WSearch) reduces the exposed attack surface but breaks indexing and search functionality across the OS and applications, and because the underlying library is shared it should not be treated as a guarantee of immunity. Note that the high attack complexity (AC:H) means exploitation is not deterministic, but this reduces neither the severity of a successful attempt nor the urgency of patching.

Affected VersionsENISA

Windows Server 2016 10.0.14393.0 <10.0.14393.9612
Windows 11 Version 26H2 10.0.26300.0 <10.0.26300.9711
Windows 10 Version 21H2 10.0.19044.0 <10.0.19044.7807
Windows Server 2016 (Server Core installation) 10.0.14393.0 <10.0.14393.9612
Windows Server 2012 (Server Core installation) 6.2.9200.0 <6.2.9200.26434
Windows 11 Version 25H2 10.0.26200.0 <10.0.26200.9711
Windows 10 Version 22H2 10.0.19045.0 <10.0.19044.7807
Windows Server 2025 10.0.26100.0 <10.0.26100.33650
Windows Server 2022 10.0.20348.0 <10.0.20348.5761
Windows 11 Version 24H2 10.0.26100.0 <10.0.26100.9711
Windows Server 2019 (Server Core installation) 10.0.17763.0 <10.0.17763.9376
Windows 10 Version 1607 10.0.14393.0 <10.0.14393.9612
Windows Server 2012 R2 (Server Core installation) 6.3.9600.0 <6.3.9600.23470
Windows 10 Version 1809 10.0.17763.0 <10.0.17763.9376
Windows 11 version 26H1 10.0.28000.0 <10.0.28000.3231
Windows 11 Version 23H2 10.0.22631.0 <10.0.22631.7652
Windows Server 2012 6.2.9200.0 <6.2.9200.26434
Windows Server 2019 10.0.17763.0 <10.0.17763.9376
Windows Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.33650
Windows Server 2012 R2 6.3.9600.0 <6.3.9600.23470

Affected Packages

euvd windows_10_version_1607 fix: 10.0.14393.9612
euvd windows_10_version_1809 fix: 10.0.17763.9376
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_2012 fix: 6.2.9200.26434
euvd windows_server_2012_r2 fix: 6.3.9600.23470
euvd windows_server_2012_r2_server_core_installation fix: 6.3.9600.23470
euvd windows_server_2012_server_core_installation fix: 6.2.9200.26434
euvd windows_server_2016 fix: 10.0.14393.9612
euvd windows_server_2016_server_core_installation fix: 10.0.14393.9612
euvd windows_server_2019 fix: 10.0.17763.9376
euvd windows_server_2019_server_core_installation fix: 10.0.17763.9376
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 20 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 vulnerability is a classic heap-based buffer overflow (CWE-122) in the Windows Search component, the indexing subsystem whose worker processes process content and query data on behalf of the operating system. A heap overflow of this class occurs when data is written beyond the bounds of a heap-allocated buffer, allowing adjacent heap metadata or objects to be corrupted; in a local privilege-escalation scenario a controlled corruption can be leveraged to redirect execution or impersonate a higher-privileged token. Because the Windows Search service typically runs with elevated (often SYSTEM) privileges while the attacker only needs PR:L, a successful corruption yields a meaningful integrity boundary crossing, which is reflected in the CVSS base metrics C:H/I:H/A:H with scope unchanged (S:U). The AC:H rating indicates that reliable corruption depends on heap grooming, allocation ordering, or timing conditions rather than a deterministic single-shot trigger, so exploitation is not guaranteed on every attempt. CPE strings were not supplied in the source data; the affected population was derived from the EUVD version ranges, which enumerate OS build thresholds across Windows 10, Windows 11, and Windows Server branches.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 7.0 HIGH
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 7.0 HIGH

Local EoP by an already-authenticated low-privilege user (AV:L/PR:L), high complexity due to heap-state dependence (AC:H), yielding SYSTEM-level code execution with full C/I/A impact.

3.1 AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
4.0 AV:L/AC:H/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
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Patch available
Oct 13, 2026 - 20:20 EUVD
CVE Published
Oct 13, 2026 - 19:20 cve.org
HIGH 7.0

DescriptionCVE.org

Heap-based buffer overflow in Microsoft Windows Search Component allows an authorized attacker to elevate privileges locally.

Executive ViewAI

Why It Matters

Microsoft Windows Search, a default component across Windows 10, Windows 11, and Windows Server, contains a high-severity local privilege escalation flaw that could let an attacker with existing low-privileged access on a host corrupt memory and elevate to a higher-integrity context. Because the issue is local-only and requires specific memory-layout conditions, it is not remotely exploitable and no public exploit has been identified; however, successful elevation on an endpoint or server could undermine least-privilege controls and enable broader credential or data access. Leadership should prioritize patching managed Windows estates to reduce insider, compromised-account, and post-exploitation risk.

Business Impact: Medium
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.3%
Top 81% exploitable
Prevalence
Ubiquitous
Windows Search ships in all affected desktop and server editions
Vendor Status
Publicly Disclosed:No
Exploited:No
Latest Software Release:Exploitation More 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 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
Medium
Technical Impact
Total

Priority Score

35
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +35
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

A heap overflow occurs when a program writes data beyond the bounds of a buffer allocated in the heap memory region.

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