Microsoft · Windows

CVE-2021-31956

Microsoft Windows NTFS Privilege Escalation Vulnerability

Evidence

Source & freshness

Full source status →

CISA KEV catalog Core KEV record

CVE, vendor/product, CISA dates, ransomware status, description, required action, and notes.

Catalog 2026.07.24 · Retrieved 2026-07-25 20:49 UTC Open official CISA feed ↗

MITRE CWE catalog CWE context

CWE names and plain-language weakness descriptions. CISA supplies the CWE assignment itself.

Retrieved 2026-07-25 20:59 UTC Open official MITRE CWE catalog ↗

National Vulnerability Database NVD technical context

CVSS metrics, NVD timeline, and related NVD record data are stored locally.

Retrieved Jul 25, 2026, 08:49 PM UTC Open NVD record ↗

CISA KEV record

CISA date added: 2021-11-03
CISA due date: 2021-11-17
Known ransomware use: Unknown

NVD risk context

7.8 HIGH

CVSS is a technical severity score. CISA’s KEV status remains the evidence that this vulnerability is known to be exploited.

View NVD record ↗

Attack vector

Local

An attacker needs local access to the affected system.

Attack complexity

Low

Exploitation does not require unusual conditions beyond normal attacker control.

Privileges required

Low

The attacker needs limited privileges before exploiting the issue.

User interaction

None

No action by another user is required.

Description

Microsoft Windows New Technology File System (NTFS) contains an unspecified vulnerability that allows attackers to escalate privileges via a specially crafted application.

Required action

Apply updates per vendor instructions.

NVD reference index

Vendor and remediation references

NVD has tagged these sources as vendor advisories, patches, mitigations, or release notes.

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31956 ↗
PatchVendor Advisory NVD reference source: secure@microsoft.com

Other NVD references (1)

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31956 ↗
US Government Resource NVD reference source: 134c704f-9b21-4f2e-91b3-4a467353bcc0

MITRE CWE context

CWE classification

CWE-191 Integer Underflow (Wrap or Wraparound)

The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

View official MITRE CWE details ↗

CWE-787 Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

View official MITRE CWE details ↗

NVD record timing

NVD record timeline

These dates describe NVD’s record, not CISA’s KEV addition or remediation due date.

NVD published: Jun 08, 2021, 11:15 PM UTC
NVD last updated: Jun 17, 2026, 03:52 AM UTC

Advanced: view the technical CVSS vector

This standardized code is intended for security tools and technical analysts. The plain-language risk summary above explains its main points.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

View NVD record ↗

CISA notes

https://nvd.nist.gov/vuln/detail/CVE-2021-31956

https://nvd.nist.gov/vuln/detail/CVE-2021-31956