Windows NTLMv2 Hash Disclosure via File Open Operations

Historical catalog analysis: CISA added this entry on November 12, 2024. The entry reflects catalog information retrieved on August 31, 2026, not a snapshot archived on the inclusion date. Check current vendor guidance before acting.

What the vulnerability is

CVE-2024-43451 is an NTLMv2 hash spoofing vulnerability affecting Microsoft Windows. The flaw resides in how the system handles certain file open operations, which can be manipulated to disclose a user’s NTLMv2 hash to an attacker. If successful, this disclosure allows an attacker to leverage the captured hash to impersonate the affected user.

Exposure and applicability

This vulnerability applies to Windows environments where users may interact with files or paths that trigger NTLM authentication. The primary exposure path is a file open operation; if a user is induced to open a malicious file or access a remote share controlled by an attacker, the system may transmit the NTLMv2 hash. This risk is particularly relevant for organizations relying on legacy NTLM authentication rather than more secure alternatives like Kerberos.

Remediation priorities

Our analysis suggests prioritizing remediation based on the level of administrative privilege held by users who frequently access external or untrusted file shares.

1. Apply Vendor Mitigations: The primary corrective action is to apply the mitigations provided by Microsoft. This should be prioritized for high-value targets and systems with broad network exposure.
2. Restrict NTLM Usage: Where possible, reducing the reliance on NTLM in favor of Kerberos can reduce the attack surface available for this specific spoofing mechanism.
3. Disable Unnecessary Outbound SMB: Restricting outbound SMB traffic to trusted destinations may limit the ability of an attacker to capture hashes via remote file open operations.

How to validate remediation

Verification must go beyond confirming that a patch was deployed or a version number was updated. To ensure exposure is actually reduced, defenders should:

• Verify Mitigation State: Confirm through configuration audits that the specific vendor-recommended registry keys or group policy settings associated with CVE-2024-43451 are active across the fleet.
• Network Traffic Analysis: Use authorized network monitoring to verify that NTLM authentication requests are not being sent to unauthorized or external IP addresses during file access tests.
• Authentication Auditing: Review security logs for unexpected NTLM authentication events originating from endpoints toward unknown remote shares.

Limits and open questions

While vendor mitigations address the vulnerability, residual risk remains if NTLM is still permitted globally across the environment. The source does not specify whether this vulnerability can be triggered via local files or requires a network-based share. Additionally, while CISA has added this to the Known Exploited Vulnerabilities catalog, it remains unknown if this flaw is currently being utilized in ransomware campaigns.

Source and editorial note

CVE-2024-43451: Microsoft Windows NTLMv2 Hash Disclosure Spoofing Vulnerability · Source date: November 12, 2024 · Retrieved August 31, 2026.

Material facts are tied to the cited primary source. Recommendations are independent defensive analysis unless attributed to the source. Confirm consequential decisions against current authoritative guidance.

Archive date: November 15, 2024. The displayed post date is assigned three days after the source date to organize this retrospective archive; it does not mean this site published the analysis then. First published by this site: November 04, 2026 at 00:30 UTC.

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