CVE-2023-24880

CVE-2023-24880: Windows SmartScreen Security Feature Bypass Vulnerability

AI-generated analysis based on the vulnerability data on this page.

Summary

CVE-2023-24880 is a security feature bypass vulnerability in Microsoft Windows SmartScreen. The flaw stems from an incorrect authorization check (CWE-863) that enables an attacker to circumvent SmartScreen's reputation-based warnings when a user attempts to execute an untrusted file. Successful exploitation allows the attacker to execute malicious code without triggering the typical "Windows protected your PC" dialog, reducing the user's opportunity to decline execution. Microsoft has assigned this a Medium severity CVSS v3.1 score of 4.4.

Background

Windows SmartScreen is a security feature introduced in Windows 8 and enhanced in subsequent releases. It uses reputation-based heuristics and Microsoft's cloud intelligence to evaluate whether files downloaded from the internet are potentially malicious. When a file lacks reputation or is known to be suspicious, SmartScreen displays a warning dialog requiring explicit user action to proceed. This layer acts as a critical social-engineering defense, particularly against phishing campaigns that deliver malware via email or web downloads.

Root Cause

The vulnerability is classified under CWE-863: Incorrect Authorization. The root cause lies in the way SmartScreen validates the trustworthiness of downloaded files prior to rendering the execution prompt. Specifically, the affected Windows versions fail to properly enforce authorization checks on file execution when certain metadata conditions are manipulated. This allows an attacker-crafted file to be treated as trusted or to bypass the warning interface entirely, even though it originated from an untrusted internet zone.

The attack complexity is low, no privileges are required, and only local access with user interaction is needed — making it an attractive target for adversaries distributing malware via social engineering.

Impact

The CVSS v3.1 metrics reflect a focused integrity and availability impact with no confidentiality compromise:

While the base score of 4.4 is Medium, the real-world risk is elevated. The extremely high EPSS score of 0.78152 (99.52nd percentile) and inclusion in both the CISA Known Exploited Vulnerabilities catalog and the EU Vulnerability Database indicate widespread, active exploitation. Attackers leverage this bypass to improve malware delivery success rates in phishing and drive-by download campaigns.

Exploitation Walkthrough

Ethics caveat: The following description is provided for defensive awareness only. No weaponized exploit code is included.

An attacker crafts a malicious executable (e.g., a signed or specially packaged binary) and delivers it to the victim via phishing email, compromised website, or removable media. When the victim attempts to run the file, the manipulated metadata causes SmartScreen to skip its reputation check and warning dialog. The executable launches directly, giving the user no opportunity to abort. This technique has been observed in the wild to deploy ransomware and information-stealing malware payloads.

Because user interaction is still required (the victim must execute the file), this vulnerability is most effectively exploited in conjunction with convincing social-engineering lures.

Affected and Patched Versions

The following Windows versions are confirmed vulnerable based on CPE data:

Windows 10

• Version 1607
• Version 1809
• Version 20H2
• Version 21H2
• Version 22H2

Windows 11

• Version 21H2
• Version 22H2

Windows Server

• Windows Server 2016
• Windows Server 2019
• Windows Server 2022

Microsoft released security updates addressing this vulnerability in March 2023. Systems that have installed the March 2023 cumulative security updates (or later) are protected.

Remediation

Primary: Apply the Microsoft security update for March 2023 (or the latest cumulative update) for all affected Windows versions. The official patch guidance is available via the Microsoft Security Response Center:

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-24880

Compensating Controls:

• Enable Application Control (WDAC/AppLocker) to restrict execution of untrusted binaries.
• Configure Microsoft Defender SmartScreen for Microsoft Edge and Microsoft Store apps to block potentially unwanted apps.
• Use Attack Surface Reduction (ASR) rules, particularly "Block executable content from email client and webmail."
• Train users to avoid executing unexpected email attachments or downloaded files, even if no SmartScreen warning appears.

Detection

Defenders should monitor for:

• Execution of binaries from internet-download locations (e.g., Downloads folder) without corresponding SmartScreen events in the Windows Event Log.
• Anomalous Event ID 5007 (Windows Defender/Security) or missing Event ID 1116 (SmartScreen detections) where they would normally be expected.
• Endpoint detection and response (EDR) alerts for unsigned or low-reputation executables launching without user-interaction prompts.
• CISA's KEV catalog cross-referencing for vulnerable asset inventories.

Assessment

CVE-2023-24880 illustrates how a Medium-severity security-feature bypass can become a high-priority threat when paired with aggressive in-the-wild exploitation. The EPSS score of 0.78152 is a strong signal that threat actors have operationalized this flaw at scale. The dual listing in both U.S. (CISA) and EU vulnerability databases underscores its cross-border impact.

Key lessons:

1. Security-feature bypasses should not be dismissed solely because of a modest CVSS base score; EPSS and KEV status provide essential context.
2. Layered controls — application control, ASR rules, and user awareness — remain critical compensating defenses when patch deployment lags.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-24880
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-24880