9.3

CVE-2021-31956: Microsoft Windows NTFS Privilege Escalation Vulnerability

CVSS: 9.3v2.0HighKEVAnalyzed
Published 08-06-2021Last modified 12-01-2026
Open JSON

Vulnerability summary

CVE-2021-31956 is a high (CVSS 9.3) Integer Underflow (Wrap or Wraparound) vulnerability in Microsoft Windows. It is known to be exploited: CISA lists it, first on 03-11-2021. EPSS estimates a 22.27% chance of exploitation in the next 30 days, higher than 97.6% of scored vulnerabilities.

Overall risk
85/100
0100
Critical · default modelHow is this calculated?
CVSS score
9.3/10
010
High · v2.0 (NVD)
EPSS score
22.27%
0%100%
High · 0.00 pp in 30 days
KEVListedCISA
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 08-06-2021
    PublishedVulnerability first disclosed.
  2. 03-11-2021
    Added to CISA KEVMicrosoft Windows NTFS Privilege Escalation Vulnerability
  3. 17-11-2021
    CISA remediation dueApply updates per vendor instructions.
  4. 12-01-2026
    Last modifiedVulnerability information updated.

Description

Windows NTFS Elevation of Privilege Vulnerability

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

22.27%

Chance of exploitation in the next 30 days

Percentile

98%

Versus all other CVEs

30-day change

0.00 pp

From 22.27% on 19-09-2026

19-09-202619-10-2026
EPSS score
22.27%

Known exploited

Compare KEV catalogs
CISA KEVListed
Added
03-11-2021
Federal due date
17-11-2021

CISA required action

Apply updates per vendor instructions. nvd.nist.gov/vuln/detail/CVE-2021-31956

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Microsoft36 products

1 vendor · 36 products

References

2 links