Cyber Resilience

CVE-2023-21539

Memory Safety in Microsoft Windows 10 20H2

Memory Safety
Published
10 January 2023
Modified
21 November 2024
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.012 64th percentile
Risk Priority 64 floored blend · peak EPSS

Summary

CVE-2023-21539 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Microsoft Windows 10 20H2. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 36% 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-2023-21539 is a remote code execution vulnerability affecting the Windows Authentication component. It carries a CVSS 3.1 base score of 7.5 and is associated with CWE-125. The flaw permits an attacker to execute arbitrary code on an affected system when specific conditions are met during authentication processing.

An authenticated user with low privileges can exploit the issue over a network connection, though successful exploitation requires high attack complexity and no user interaction. Successful attacks can result in full compromise of confidentiality, integrity, and availability on the target system.

Microsoft security advisories for CVE-2023-21539, available at the referenced MSRC update guide, detail the affected Windows versions and the corresponding security updates that address the vulnerability.

The EPSS score for this CVE rose from lower values to a peak of 0.0976 on 2025-01-22 before receding to the current 0.0305, indicating a period of increased exploitation interest after disclosure.

EU & UK References

Vulnerability Data

Windows Authentication Remote Code Execution Vulnerability

CWE(s)
CWE-125NVD-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 →
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
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-2023-21819Same product: Microsoft Windows 10 20H2
CVE-2023-35357Same product: Microsoft Windows 10 21H2
CVE-2023-36696Same product: Microsoft Windows 10 21H2
CVE-2024-26172Same product: Microsoft Windows 10 21H2
CVE-2023-21729Same product: Microsoft Windows 10 20H2
CVE-2023-24872Same product: Microsoft Windows 10 20H2
CVE-2023-35358Same product: Microsoft Windows 10 21H2
CVE-2024-29994Same product: Microsoft Windows 10 21H2
CVE-2023-24924Same product: Microsoft Windows 10 20H2
CVE-2023-21769Same product: Microsoft Windows 10 20H2

Affected Assets

microsoft
windows 10 20h2
all versions
microsoft
windows 10 21h2
all versions
microsoft
windows 10 22h2
all versions
microsoft
windows 11 21h2
all versions
microsoft
windows 11 22h2
all versions
microsoft
windows server 2022
all versions

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 mostly match
prevents

Secure-development practices such as bounds checking and memory-safe languages directly prevent out-of-bounds reads.

ID.RA-01 partial match
prevents

Vulnerability scanning and recording can discover instances of out-of-bounds reads after code is deployed.

PR.PS-02 partial match
prevents

Routine patching replaces vulnerable code containing out-of-bounds read flaws.

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 and acceptance includes fuzzing and static analysis that detect out-of-bounds read defects before release.

A.8.15 Logging partial match
finds

Logging can record evidence of an out-of-bounds read but does not prevent the weakness itself.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates input validation and bounds checking that directly prevent out-of-bounds reads.

A.8.26 Application security requirements partial match
prevents

Application security requirements include explicit bounds and memory-safety specifications that mitigate buffer over-reads.

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

Secure system architecture and engineering principles require memory-safe design patterns and runtime protections against out-of-bounds access.

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly forbid unsafe pointer arithmetic and mandate bounds-checked reads, eliminating CWE-125.

References