Security 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 0.22 98th percentile
Risk Priority 83 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

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 LSASS Memory (T1003.001); ranked in the top 2% 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

T1003.001 LSASS Memory Credential Access
Adversaries may attempt to access credential material stored in the process memory of the Local Security Authority Subsystem Service (LSASS).
attack.mitre.org →
T1003.003 NTDS Credential Access
Adversaries may attempt to access or create a copy of the Active Directory domain database in order to steal credential information, as well as obtain other information about domain members such as devices, users, and access rights.
attack.mitre.org →
T1003.005 Cached Domain Credentials Credential Access
Adversaries may attempt to access cached domain credentials used to allow authentication to occur in the event a domain controller is unavailable.
attack.mitre.org →
T1003.008 /etc/passwd and /etc/shadow Credential Access
Adversaries may attempt to dump the contents of <code>/etc/passwd</code> and <code>/etc/shadow</code> to enable offline password cracking.
attack.mitre.org →
T1005 Data from Local System Collection
Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.
attack.mitre.org →
T1008 Fallback Channels Command And Control
Adversaries may use fallback or alternate communication channels if the primary channel is compromised or inaccessible in order to maintain reliable command and control and to avoid data transfer thresholds.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

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
CVE-2021-34486Same product: Microsoft Windows 10 1809both 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.

ID.RA-01 partial match
blocks

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

PR.PS-02 partial match
blocks

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

PR.PS-06 partial match
blocks

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

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.5.14 Information transfer partial match
removes
A.5.15 Access control partial match
removes
A.5.16 Identity management partial match
removes
A.5.17 Authentication information partial match
removes
A.5.18 Access rights partial match
removes
A.8.10 Information deletion partial match
removes

References