Cyber Resilience

CVE-2021-31956

Memory Safety in Microsoft Windows Server 2008 r2 … sp2

CISA KEVActive ExploitationEUVD ExploitedMemory Safety
Published
08 June 2021
Modified
12 January 2026
KEV Added
03 November 2021
Patch / advisory
View advisory
CVSS Score v3.1 7.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.20 97th percentile
Risk Priority 83 floored blend · peak EPSS

Summary

CVE-2021-31956 is a high-severity Wrap or Wraparound (CWE-191) vulnerability in Microsoft Windows Server 2008. Its CVSS base score is 7.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 3% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2021-31956 is an elevation of privilege vulnerability in the Windows NTFS component, assigned CWE-191 and carrying a CVSS 3.1 score of 7.8. It affects Microsoft Windows systems that use the NTFS file system.

An attacker with local access and low privileges can exploit the flaw without user interaction to achieve full elevation of privilege, resulting in high impact to confidentiality, integrity, and availability on the target system.

Microsoft has published security guidance and patches for the issue through its advisory portal. The vulnerability is also listed in CISA's catalog of known exploited vulnerabilities, confirming observed in-the-wild exploitation.

EU & UK References

Vulnerability Data

Windows NTFS Elevation of Privilege Vulnerability

CWE(s)
CWE-191
KEV Date Added
03 November 2021

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2021-31979Same product: Microsoft Windows 10 1507both on KEV
CVE-2021-40449Same product: Microsoft Windows 10 1507both on KEV
CVE-2021-33742Same product: Microsoft Windows 10 1507both on KEV
CVE-2021-34448Same product: Microsoft Windows 10 1507both on KEV
CVE-2020-17087Same product: Microsoft Windows 10 1507both on KEV
CVE-2021-26411Same product: Microsoft Windows 10 1507both on KEV
CVE-2022-41033Same product: Microsoft Windows 10 1507both on KEV
CVE-2022-24521Same product: Microsoft Windows 10 1507both on KEV
CVE-2020-0674Same product: Microsoft Windows 10 1507both on KEV
CVE-2021-40444Same product: Microsoft Windows 10 1507both on KEV

Affected Assets

microsoft
windows 10 1507
≤ 10.0.10240.18967
microsoft
windows 10 1607
≤ 10.0.14393.4467
microsoft
windows 10 1809
≤ 10.0.17763.1999
microsoft
windows 10 1909
≤ 10.0.18363.1621
microsoft
windows 10 2004
≤ 10.0.19041.1052
microsoft
windows 10 20h2
≤ 10.0.19042.1052
microsoft
windows 10 21h1
≤ 10.0.19043.1052
microsoft
windows 7
all versions
microsoft
windows 8.1
all versions
microsoft
windows rt 8.1
all versions
+6 more product configuration(s) — see NVD for full list

Mitigating Controls

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 full match
prevents

Secure SDLC practices directly prevent integer underflow defects via input validation, bounds checking, and static analysis.

ID.RA-01 partial match
prevents

Vulnerability scanning and code analysis can surface underflow flaws after they are introduced.

PR.PS-02 partial match
prevents

Routine patching can remediate known underflow bugs once they are discovered in deployed software.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development catches integer underflow defects before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and arithmetic checks that prevent integer underflow.

A.8.26 Application security requirements partial match
prevents

Application security requirements include bounds checking and safe arithmetic to avoid underflow conditions.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles require defensive coding patterns that mitigate integer wraparound risks.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prescribe safe integer handling and overflow/underflow prevention.

References