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Medium

Windows File Explorer NTLM Hash Leakage / Spoofing Bypass

IdentifiersCVE-2025-59214CWE-200· Exposure of Sensitive Information…

CVE-2025-59214 is a Windows File Explorer vulnerability described by Microsoft as an exposure of sensitive information to an unauthorized actor that allows spoofing over a network. Based on the provided content, the issue is associated with File Explorer previewing internet-downloaded files marked with Mark of the Web (MotW). A crafted file containing HTML-like tags such as <link> or <src> that reference attacker-controlled external paths can cause Windows to initiate outbound authentication, leaking NTLM credential material over the network. The content indicates this issue is part of a bypass chain: CVE-2025-59214 bypasses the fix for CVE-2025-50154, which itself bypassed the earlier CVE-2025-24054 zero-click NTLM leakage issue. Microsoft’s October 2025 mitigation disables File Explorer preview-pane rendering for MotW-tagged files to prevent this credential leakage path.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can expose NTLM authentication hashes to an attacker-controlled remote system. Those leaked credentials can then be used for offline password cracking or NTLM relay attacks, enabling follow-on spoofing, unauthorized access, and potential lateral movement depending on the victim account’s privileges and the target environment. The vulnerability therefore creates a credential exposure condition rather than direct code execution, but it can materially facilitate network compromise.

Mitigation

If you can’t patch tonight, do this now.

Until patches are fully deployed, reduce exposure by preventing users from previewing or interacting with untrusted downloaded files and email attachments, especially files carrying Mark of the Web. Restrict or monitor outbound SMB/NTLM authentication to untrusted hosts, disable or limit NTLM where operationally feasible, and enforce protections against NTLM relay. User awareness and attachment-handling controls can further reduce risk. The provided content also notes that users can manually remove the block via the file Properties dialog using Unblock, so organizations should control or discourage that action for untrusted files.

Remediation

Patch, then assume compromise.

Apply Microsoft’s October 2025 security updates that disable File Explorer preview rendering for internet-downloaded files marked with Mark of the Web. Ensure systems are updated beyond the earlier incomplete fixes for CVE-2025-24054 and CVE-2025-50154, as CVE-2025-59214 is described as a subsequent bypass. After patching, verify the new File Explorer behavior is active, noting Microsoft stated the change may not take effect until the next user logon.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Microsoft CorporationWindows 10 1507operating_system
Microsoft CorporationWindows 10 1607operating_system
Microsoft CorporationWindows 10 1809operating_system
Microsoft CorporationWindows 10 21h2operating_system
Microsoft CorporationWindows 10 22h2operating_system
Microsoft CorporationWindows 11 22h2operating_system
Microsoft CorporationWindows 11 23h2operating_system
Microsoft CorporationWindows 11 24h2operating_system
Microsoft CorporationWindows 11 25h2operating_system
Microsoft CorporationWindows 11 2h2operating_system
Microsoft CorporationWindows Server 2008operating_system
Microsoft CorporationWindows Server 2008 R2operating_system
Microsoft CorporationWindows Server 2008 Sp2operating_system
Microsoft CorporationWindows Server 2012operating_system
Microsoft CorporationWindows Server 2012 R2operating_system
Microsoft CorporationWindows Server 2016operating_system
Microsoft CorporationWindows Server 2019operating_system
Microsoft CorporationWindows Server 2022operating_system
Microsoft CorporationWindows Server 2022 23h2operating_system
Microsoft CorporationWindows Server 2025operating_system
Microsoft CorporationWindows Server 23h2operating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

What this page doesn’t show

The version that knows your environment.

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity

Community discussion across Reddit, Mastodon, and other social sources.