Cyber Resilience

CVE-2023-21716

Memory Safety in Microsoft Sharepoint Server 2019

High EPSSMemory Safety
Published
14 February 2023
Modified
21 November 2024
Patch / advisory
View advisory
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.82 99.6th percentile
Risk Priority 97 floored blend · peak EPSS

Summary

CVE-2023-21716 is a critical-severity Integer Overflow or Wraparound (CWE-190) vulnerability in Microsoft Sharepoint Server. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 0.4% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV 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-2023-21716 is a remote code execution vulnerability in Microsoft Word, carrying a CVSS 3.1 base score of 9.8 that reflects an integer overflow weakness (CWE-190) reachable over the network without authentication or user interaction. The flaw affects the Word application component and can result in complete loss of confidentiality, integrity, and availability on the target system.

An unauthenticated attacker positioned on the network can send a specially crafted document or request that triggers the flaw, allowing arbitrary code execution with the privileges of the Word process and full control over the affected host.

Microsoft security advisories published at the MSRC update guide for this CVE describe the available patches and urge customers to apply the fixes promptly to eliminate the exposure.

The associated EPSS score remains at a high level near 0.91 with no indicated rise from a low baseline.

EU & UK References

Vulnerability Data

Microsoft Word Remote Code Execution Vulnerability

CWE(s)
CWE-190NVD-CWE-noinfo

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 →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-21379Same product: Microsoft Office
CVE-2023-35372Same product: Microsoft Office
CVE-2023-36866Same product: Microsoft Office
CVE-2023-28295Same product: Microsoft Office
CVE-2025-21338Same product: Microsoft Office
CVE-2026-55026Same product: Microsoft Sharepoint Server
CVE-2026-44812Same product: Microsoft Word
CVE-2026-44803Same product: Microsoft Word
CVE-2024-21450Same vendor: Microsoft
CVE-2025-21243Same vendor: Microsoft

Affected Assets

microsoft
office
2019
microsoft
office long term servicing channel
2021
microsoft
office online server
2016
microsoft
office web apps
2013
microsoft
sharepoint enterprise server
2013, 2016
microsoft
sharepoint foundation
2013
microsoft
sharepoint server
2019, all versions
microsoft
word
2013

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V5.2.6

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 mostly match
prevents

Secure SDLC practices directly require use of safe arithmetic, bounds checks, and testing that prevent integer overflows.

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 can detect integer overflows before release.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates input validation and arithmetic checks that prevent integer overflows.

A.8.26 Application security requirements partial match
degrades

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

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

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

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly forbid unsafe integer operations and mandate overflow-safe constructs.

References