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Windows BitLocker CVE-2026-96909

| EUVDEUVD-2026-100238 CRITICAL
Heap-based Buffer Overflow (CWE-122)
2026-10-13 secure@microsoft.com GHSA-f44g-f5v6-h7gj
9.8
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
    Reach exposed BitLocker network path
  2. Delivery
    Send crafted overflow request
  3. Exploit
    Corrupt heap memory (CWE-122)
  4. Execution
    Execute arbitrary code
  5. Impact
    Full compromise of Windows host

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

Per the supplied CVSS vector (AV:N/AC:L/PR:N/UI:N) there are no authentication or user-interaction prerequisites, implying remote unauthenticated exploitation of affected Windows builds (Windows 11 23H2-26H2, Windows Server 2022/2025 below the patched build numbers listed in EUVD). The practical limiting factor is reachability of the vulnerable BitLocker code path: BitLocker is a full-disk-encryption feature typically exercised locally or during pre-boot/recovery, so network exploitation likely requires the host to expose that specific path (e.g., a network-facing pre-boot, recovery, or management scenario) rather than any default service - this should be confirmed against the MSRC advisory, as it materially narrows exposure versus a generic internet-facing service.

Impact

Multiple signals point to high priority but with one notable internal tension. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N, base 9.8) describes remote, unauthenticated, low-complexity exploitation with total CIA impact, and the CWE-122 heap overflow with a 'total' SSVC technical impact reinforces a full-system-compromise outcome. SSVC also marks the flaw Automatable:yes, meaning it could be reliably scripted/wormed if a working exploit emerges. Counterbalancing this, SSVC Exploitation is 'none', there is no CISA KEV listing and no public POC, so no public exploit identified at time of analysis - real-world pressure is currently theoretical despite the critical score. The key conflict to flag: the affected component is Windows BitLocker, a full-disk-encryption feature normally reached locally or at pre-boot, yet the description and CVSS assert code execution 'over a network' (AV:N). This network reachability for an encryption component is atypical and should be verified against Microsoft's MSRC advisory before assuming broad remote exposure; it may depend on a specific recovery/pre-boot or management path rather than the general network. Net: treat as critical for patching given ubiquitous Windows footprint and total impact, but current exploitation likelihood is lower than the 9.8 alone implies.

Exploit ScenarioDerived

An unauthenticated attacker with network reachability to a vulnerable BitLocker code path sends a crafted request that overflows a heap buffer (CWE-122), corrupting memory to achieve arbitrary code execution on the target Windows host. Because CVSS rates attack complexity low and no privileges or user interaction are required, a reliable exploit would need no victim action - though no public POC or active exploitation is known at time of analysis.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 0.9% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 13, 2026

Remote code execution in Windows BitLocker is possible through a heap-based buffer overflow (CWE-122) that carries a 9.8 CVSS rating with the vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H, meaning unauthenticated remote attackers need no user interaction to trigger memory corruption that can yield full compromise of confidentiality, integrity, and availability on affected unpatched builds. Affected platforms include Windows 11 versions 23H2 through 26H2 (and 26H1), Windows Server 2022, and Windows Server 2025 including Server Core installations running builds below the patched thresholds listed by EUVD. There is no public exploit identified at time of analysis and CISA's SSVC assessment records exploitation as 'none', though it flags the issue as automatable with total technical impact; the practical constraint is reachability, since BitLocker is a full-disk-encryption component normally exercised locally or during pre-boot/recovery rather than exposed as a default network service.

RemediationAI

Patch available per vendor advisory: Microsoft has published fixes through the MSRC update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-96909, and administrators should apply the current cumulative updates so each system reaches or exceeds the patched build thresholds indicated by the EUVD ranges - Windows Server 2022 at 10.0.20348.5761, Windows 11 23H2 at 10.0.22631.7652, 24H2 at 10.0.26100.9711, 25H2 at 10.0.26200.9711, 26H2 at 10.0.26300.9711, 26H1 at 10.0.28000.3231, and Windows Server 2025 including Server Core at 10.0.26100.33650 - or later. Until patching is complete, the highest-value compensating control follows from the reachability caveat in the assessment: restrict network access to any BitLocker-related pre-boot, recovery, or management interface by segmenting management networks, disabling network boot or remote WinRE/recovery paths where they are not operationally required, and placing any recovery or management service behind VPN or strict allow-listing, accepting the trade-off that legitimate recovery workflows may require temporary re-enablement; additionally consider tightening host firewall rules and monitoring for anomalous connections to BitLocker/recovery-related endpoints. Because SSVC rates this flaw as automatable with total technical impact, prioritize patching internet-reachable and management-plane Windows 11 23H2-26H2 and Windows Server 2022/2025 systems first, and validate exposure rather than assuming the BitLocker path is reachable on every host, since exploitation is not confirmed as active at time of analysis.

Affected VersionsENISA

Windows Server 2022 10.0.20348.0 <10.0.20348.5761
Windows 11 Version 26H2 10.0.26300.0 <10.0.26300.9711
Windows 11 Version 25H2 10.0.26200.0 <10.0.26200.9711
Windows 11 Version 24H2 10.0.26100.0 <10.0.26100.9711
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 2025 10.0.26100.0 <10.0.26100.33650
Windows Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.33650

Affected Packages

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 8 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 heap-based buffer overflow (CWE-122), a memory-safety class in which a heap-allocated buffer is written past its bounds, corrupting adjacent heap metadata or objects and typically enabling controlled memory corruption that can be steered into arbitrary code execution under the privileges of the vulnerable process. The affected component is BitLocker, Microsoft's full-disk-encryption (FDE) subsystem that integrates with the TPM, pre-boot authentication, recovery key handling, and WinRE-based recovery flows on Windows client and server SKUs; the EUVD data maps the affected builds as Windows Server 2022 10.0.20348.0, Windows 11 23H2 10.0.22631.0, 24H2 10.0.26100.0, 25H2 10.0.26200.0, 26H1 10.0.28000.0, 26H2 10.0.26300.0, and Windows Server 2025 (including Server Core) 10.0.26100.0. Because the assessed vector is AV:N/AC:L/PR:N/UI:N, the vulnerable code path is treated as remotely reachable with no authentication and no user interaction, which is unusual for an FDE component and implies the overflowing parser or handler is exposed through some network-facing BitLocker-related surface (for example a pre-boot, recovery, or management scenario) rather than through routine local disk operations; confirming that specific reachable interface against the MSRC advisory is important because it materially narrows real-world exposure relative to a conventional internet-facing service. The root cause remains a classic unsafe length or bounds check on attacker-influenced input in a heap buffer, and exploitation potential is amplified on builds lacking the vendor fix because heap corruption in a privileged Windows component can bypass typical application-level containment.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
ENISA EUVD HIGH
vuln.today AI 9.8 CRITICAL

Description states unauthenticated network code execution (AV:N/PR:N/UI:N) via heap overflow yielding full RCE, so C/I/A:H; scope unchanged as code runs on the same host.

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

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
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 - 19:22 cve.org
CRITICAL 9.8

DescriptionCVE.org

Heap-based buffer overflow in Windows BitLocker allows an unauthorized attacker to execute code over a network.

Executive ViewAI

Why It Matters

A critical heap-based buffer overflow in Microsoft's BitLocker full-disk encryption component (CVE-2026-96909) affects Windows 11 builds 23H2 through 26H2 and 26H1, Windows Server 2022, and Windows Server 2025 including Server Core, and would let an unauthenticated remote attacker gain full control of confidentiality, integrity, and availability on unpatched systems with no user interaction required. No public exploit code and no confirmed active exploitation have been identified (CISA SSVC exploitation: none), but the flaw is rated automatable with total technical impact, so the practical risk depends on how widely BitLocker management, recovery, or pre-boot interfaces are reachable across the network. Because BitLocker underpins data-at-rest protection for the endpoint and server estate, leadership should treat patch completion as a near-term compliance and resilience obligation rather than a routine update.

Business Impact: High
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.9%
Top 41% exploitable
Prevalence
Ubiquitous
BitLocker ships in Windows Pro/Enterprise and Server across most environments
Threat Intel
1
1 sources
Vendor Status
Publicly Disclosed:No
Exploited:No
Latest Software Release:Exploitation Less Likely
Data Quality
6 sources
Confidence: High

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 0.9%
Patch available Yes
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

55
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +49
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: +5

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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