CVE-2025-24991: Microsoft Windows NTFS Out-Of-Bounds Read Vulnerability

CVE-2025-24991 is an out-of-bounds read vulnerability in the Microsoft Windows New Technology File System (NTFS). An authorized attacker with local access can use it to disclose information from the system.

Information disclosure flaws of this type matter because they can reveal memory contents, configuration details, or other sensitive data that help an attacker plan follow-on actions. Because the vulnerability requires local authorization, it is most relevant on multi-user systems, shared workstations, or environments where untrusted code or users already have a foothold.

How it works

The underlying weakness is CWE-125 (out-of-bounds read). In this class of flaw, software reads data past the end of an allocated buffer or structure. When the Windows NTFS component mishandles certain inputs or operations, an authorized local attacker can trigger a read that returns data outside the intended bounds.

The result is information disclosure rather than remote code execution. The attacker does not need to invent complex network payloads; they need only local access and the ability to interact with the affected NTFS path or interface. Exact trigger conditions and any required privileges must be confirmed against the vendor advisory; public detail beyond the CISA summary is limited.

Am I affected? How to find it in your systems

Microsoft Windows systems that use NTFS are in scope. NTFS is the default file system on the vast majority of Windows client and server installations, so the vulnerability potentially applies broadly across enterprise fleets.

• Inventory all Windows endpoints and servers via your asset management, CMDB, or endpoint management platform. Note build and update levels.
• Compare installed updates against the Microsoft security advisory for CVE-2025-24991. Confirm the exact fixed builds and any version or configuration caveats listed there; do not rely on third-party summaries alone.
• On systems that cannot be patched immediately, review local security logs and EDR telemetry for unusual NTFS-related activity, unexpected process access to volume metadata, or local privilege-escalation attempts that might precede or follow information disclosure.
• Pay particular attention to multi-user machines, jump hosts, developer workstations, and any systems where non-administrative users or untrusted processes already run.

Because exploitation is local, network scanners will not detect the vulnerability itself; host-based inventory and patch status are the primary indicators of exposure.

How to remediate

The primary remediation is to apply the security update provided by Microsoft for this CVE. Follow the vendor instructions exactly, including any prerequisite updates or reboot requirements.

• Deploy the patch through your standard Windows Update, WSUS, Microsoft Endpoint Manager, or equivalent channel as soon as testing confirms compatibility.
• After installation, verify the update is present on a representative sample of systems and re-check the advisory for any residual risk notes.
• As general hardening for this class of local information-disclosure issues, enforce least privilege so that ordinary users and processes cannot freely interact with sensitive NTFS interfaces, keep systems current with cumulative updates, and restrict the ability of untrusted code to run with elevated or interactive rights.

CISA guidance for this vulnerability is to apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Confirm all version-specific details against the official Microsoft advisory.

If you can't patch immediately

Until the vendor update can be applied, reduce the attack surface with compensating controls appropriate to a local out-of-bounds read:

• Limit interactive and local logon rights to only those accounts that require them. Remove unnecessary local administrator privileges.
• Use application control or allow-listing to prevent untrusted binaries and scripts from executing on high-value hosts.
• Segment critical systems so that a compromised low-privilege workstation cannot easily reach domain controllers, servers holding sensitive data, or other high-value targets.
• Increase monitoring and alerting on local process creation, unusual file-system metadata access, and EDR detections related to information-disclosure or local exploitation techniques.
• Where virtual patching or host-based intrusion prevention can intercept the specific NTFS interaction, enable those signatures after validating them against the vendor description; note that pure network WAF controls are generally ineffective against local file-system flaws.

These measures lower risk but do not eliminate it. Prioritize patching as soon as operationally feasible.

If your data may have been exposed

Actively exploited vulnerabilities can lead to broader compromise and data exposure even when the initial flaw is only information disclosure. If you have reason to believe systems were targeted before patching, treat the incident according to your standard response process: isolate affected hosts, preserve forensic evidence, and assess what data may have been accessible to the attacker.

You can also run a free exposure scan of your email addresses against known breach data sets to determine whether credentials or personal information associated with your organization already appear in public breach corpora. Combine that check with internal log review and endpoint forensics for a more complete picture.