CVE-2024-38217
Microsoft Windows Mark of the Web (MOTW) Protection Mechanism Failure Vulnerability
Description
CVE-2024-38217 is a medium-severity security feature bypass vulnerability in the Windows Mark of the Web (MotW) mechanism affecting virtually all supported versions of Windows 10, Windows 11, and Windows Server. The flaw allows a remote attacker to craft a file that bypasses the MotW security protections, which normally warn users and restrict execution of files downloaded from the internet. With an EPSS score of 12.1% (93.7th percentile), this vulnerability has been actively exploited in the wild and is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog with a remediation deadline of October 1, 2024. Security researchers at Elastic have published a detailed exploit analysis demonstrating how the bypass works in practice.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:LOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| microsoft | windows 10 1507 | < 10.0.10240.20766 |
| microsoft | windows 10 1607 | < 10.0.14393.7336 |
| microsoft | windows 10 1809 | < 10.0.17763.6293 |
| microsoft | windows 10 21h2 | < 10.0.19044.4894 |
| microsoft | windows 10 22h2 | < 10.0.19045.4894 |
| microsoft | windows 11 21h2 | < 10.0.22000.3197 |
| microsoft | windows 11 22h2 | < 10.0.22621.4169 |
| microsoft | windows 11 23h2 | < 10.0.22631.4169 |
| microsoft | windows 11 24h2 | < 10.0.26100.1742 |
| microsoft | windows server 2008 | -; r2 |
| microsoft | windows server 2012 | -; r2 |
| microsoft | windows server 2016 | < 10.0.14393.7336 |
| microsoft | windows server 2019 | < 10.0.17763.6293 |
| microsoft | windows server 2022 | < 10.0.20348.2700 |
| microsoft | windows server 2022 23h2 | < 10.0.25398.1128 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-38217(Patch, Vendor Advisory)
- https://www.elastic.co/security-labs/dismantling-smart-app-control(Exploit, Third Party Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-38217(US Government Resource)
Weakness Type
Mark of the Web Security Feature Bypass
Although no formal CWE has been assigned to CVE-2024-38217, the vulnerability represents a security feature bypass in the Windows Mark of the Web (MotW) subsystem. MotW is a critical Windows security mechanism that tags files downloaded from the internet with a Zone.Identifier alternate data stream (ADS), causing Windows to display warnings, enforce Protected View in Office applications, and trigger SmartScreen reputation checks. When this mechanism is bypassed, files downloaded from untrusted sources execute without any security prompts, effectively negating one of Windows' primary defenses against social engineering and drive-by download attacks.
Learn more: CWE-693: Protection Mechanism Failure
Impact Analysis
The CVSS v3.1 base score of 5.4 (Medium) with a vector reflecting low integrity and availability impact may seem moderate, but the real-world consequences of this vulnerability are significant. The integrity impact (I:L) indicates that an attacker can partially modify security-relevant data — specifically, circumventing the MotW tag that would otherwise trigger security warnings. The availability impact (A:L) reflects the potential for limited disruption to system protections. The attack requires user interaction (opening a crafted file) but no authentication, making social engineering the primary delivery mechanism.
From a business perspective, the Mark of the Web is a foundational layer of Windows endpoint security that many organizations depend on as a first line of defense against phishing and malware distribution. Its bypass renders downstream protections ineffective: SmartScreen checks may not trigger, Office Protected View may not engage, and application control policies that rely on MotW tags may fail. The EPSS score of 12.1% at the 93.7th percentile confirms elevated exploitation activity. While the ransomware association is listed as unknown, MotW bypasses are a known precursor to ransomware delivery chains where attackers distribute malicious Office documents or executables via email.
Exploit Maturity
CVE-2024-38217 has been confirmed as actively exploited in the wild, resulting in its addition to CISA's Known Exploited Vulnerabilities (KEV) catalog with a federal remediation deadline of October 1, 2024. The EPSS probability of 12.1% at the 93.7th percentile indicates significant exploitation activity compared to the broader vulnerability landscape. Elastic Security Labs published a comprehensive technical analysis of how the MotW bypass operates, demonstrating that the vulnerability can be weaponized as part of a broader attack chain to deliver malware past Smart App Control and SmartScreen defenses.
The ransomware usage status is classified as "Unknown," but Mark of the Web bypasses have historically been favored by threat actors distributing ransomware and information stealers through phishing campaigns. The availability of detailed exploit research combined with active exploitation makes this a high-priority patching target. Microsoft has addressed this vulnerability in the September 2024 Patch Tuesday updates, providing fixes across all affected Windows versions.
Remediation
- Apply September 2024 Patch Tuesday updates — Install the latest cumulative security updates from Microsoft for all affected Windows versions. Consult the Microsoft Security Advisory for specific KB article numbers and version requirements for each Windows edition.
- Prioritize endpoint patching — Focus remediation efforts on workstations and user-facing systems where employees are most likely to open files downloaded from the internet. These endpoints represent the highest risk from MotW bypass attacks.
- Strengthen email and web filtering — Enhance email gateway rules to quarantine or strip potentially malicious attachments (LNK files, ISO/IMG containers, Office documents with macros) that are commonly used in MotW bypass attack chains. Update web proxy policies to block downloads of high-risk file types from untrusted sources.
- Enable Attack Surface Reduction (ASR) rules — Deploy Microsoft Defender ASR rules that block execution of potentially obfuscated scripts, Office applications from creating child processes, and executable content from email. These provide defense-in-depth even when MotW protections are bypassed.
- Educate users on phishing awareness — Reinforce training around the dangers of opening files from unknown sources, particularly when security warnings are absent. Users should report suspicious files that execute without the expected Windows security prompts.
Technical Details
The CVSS v3.1 vector for CVE-2024-38217 is CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L, yielding a base score of 5.4 (Medium). Attack Vector (AV:N) indicates remote exploitation is possible, typically via a malicious file delivered over email or web download. Attack Complexity (AC:L) means no special conditions are needed beyond crafting the malicious file. Privileges Required (PR:N) confirms no authentication is needed. User Interaction (UI:R) requires the victim to open or interact with the crafted file. Scope (S:U) limits the impact to the affected component. Confidentiality (C:N) shows no data exposure, while Integrity (I:L) and Availability (A:L) reflect the bypass of security tags and limited service disruption.
The vulnerability targets the Windows Mark of the Web (MotW) implementation, which uses NTFS Alternate Data Streams to store Zone.Identifier metadata on downloaded files. When a file is downloaded from the internet (Zone 3), Windows attaches a ZoneId=3 marker that triggers security checks when the file is opened. The flaw in CVE-2024-38217 allows an attacker to construct a file that either strips, fails to inherit, or circumvents the MotW tag during processing. As demonstrated by Elastic Security Labs' research on Smart App Control bypass techniques, the vulnerability can be leveraged to execute binaries and scripts without triggering SmartScreen reputation checks or Windows Defender Application Control (WDAC) policies that depend on MotW metadata. This makes it particularly dangerous in combination with other vulnerabilities or social engineering tactics.
Frequently Asked Questions
What is CVE-2024-38217?
CVE-2024-38217 is a security feature bypass vulnerability in the Windows Mark of the Web (MotW) mechanism. It allows attackers to craft files that circumvent the MotW security tags normally applied to files downloaded from the internet, effectively bypassing SmartScreen warnings and other protective measures that rely on these tags.
Which Windows versions are affected by CVE-2024-38217?
Virtually all currently supported Windows versions are affected, including Windows 10 (versions 1507 through 22H2), Windows 11 (versions 21H2 through 24H2), and Windows Server editions from 2008 through 2022 23H2. Organizations should apply the September 2024 security updates across their entire Windows fleet.
How is CVE-2024-38217 exploited in attacks?
Attackers craft malicious files (such as executables, scripts, or Office documents) that bypass the MotW zone identifier. When a victim downloads and opens such a file, Windows does not display the usual security warnings or enforce Protected View, allowing the malicious content to execute without the user's informed consent.
Is CVE-2024-38217 used in ransomware attacks?
While the official KEV listing classifies ransomware association as "Unknown," Mark of the Web bypasses are a well-known technique in ransomware delivery chains. Threat actors frequently use MotW bypass vulnerabilities to distribute malicious payloads via phishing emails without triggering Windows security prompts.
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