CVE-2020-16877 — Windows Elevation of Privilege Vulnerability

Executive Summary

An elevation of privilege vulnerability exists when Microsoft Windows improperly handles reparse points. An attacker who successfully exploited this vulnerability could overwrite or delete a targeted file that would normally require elevated permissions. To exploit this vulnerability, an attacker would first have to log on to the system. An attacker could then run a specially crafted application that could exploit the vulnerability and overwrite or delete files. The security update addresses the vulnerability by correcting how Windows handles reparse points.

Overview

7.1

CVSS HIGH

Important

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Elevation of Privilege

Released Oct 13 2020

Last Updated Oct 13 2020

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.00958 — 0.58393 percentile

NVD CVSS 7.1 HIGH — matches MSRC

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H/E:P/RL:O/RC:C

ATTACK VECTOR

Local

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

Low

USER INTERACTION

None

SCOPE

Unchanged

CONFIDENTIALITY

None

INTEGRITY

High

AVAILABILITY

High

EXPLOIT CODE MATURITY

Proof-of-Concept

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 6.4

EPSS Score

0.00958

probability of exploitation in the next 30 days

0.58393 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

12 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 Version 1903 for 32-bit Systems	`4577671 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1903 for ARM64-based Systems	`4577671 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1903 for x64-based Systems	`4577671 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1909 for 32-bit Systems	`4577671 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1909 for ARM64-based Systems	`4577671 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1909 for x64-based Systems	`4577671 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 2004 for 32-bit Systems	`4579311 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 2004 for ARM64-based Systems	`4579311 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 2004 for x64-based Systems	`4579311 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server, version 1903 (Server Core installation)	`4577671 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server, version 1909 (Server Core installation)	`4577671 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server, version 2004 (Server Core installation)	`4579311 (Security Update)`	Important	Elevation of Privilege	Yes

Patches

2 patches

Article	Type	Restart
`4577671`	Security Update	Yes
`4579311`	Security Update	Yes

Exploits & PoC

No public exploit or PoC has been linked for this CVE yet. When available, references are sourced from public repositories and may be unverified or non-functional — review carefully before use.

Detection Rules

No public Sigma or Nuclei detection rule has been mapped to this CVE yet. Coverage is concentrated on exploited / high-profile vulnerabilities; check SigmaHQ for updates.

Acknowledgments

Donato Ferrante of IOActive

References

MSRC Advisory MITRE NVD