CVE-2021-31187

SYSTEM privilege escalation via directory junction

Published May 11, 2021 · Updated Aug 3, 2024

Privilege escalation in affected Microsoft Windows 10 releases allows local users to execute code as SYSTEM through WalletService. WalletService follows an attacker-created directory junction when creating a file, redirecting the privileged write to an arbitrary location. Exploitation requires prior low-privileged code execution on the target, and successful abuse grants SYSTEM-context code execution.

CVSS severity7.8
High
EPSS probability1.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privilege escalation in affected Microsoft Windows 10 releases allows local users to execute code as SYSTEM through WalletService. WalletService follows an attacker-created directory junction when creating a file, redirecting the privileged write to an arbitrary location. Exploitation requires prior low-privileged code execution on the target, and successful abuse grants SYSTEM-context code execution.

The record

CVE
CVE-2021-31187
Published
May 11, 2021
Updated
Aug 3, 2024
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
CWE-59, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.0 <10.0.10240.18931

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.0 <10.0.10240.18931
Microsoft · Windows 10 Version 1909version=10.0.0 <10.0.18363.1556
Microsoft · Windows 10 Version 1803version=10.0.0 <10.0.17134.2207
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19042.982
Microsoft · Windows 10 Version 1607version=10.0.0 <10.0.14393.4401
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19041.982
Microsoft · Windows 10 Version 1809version=10.0.0 <10.0.17763.1935

Published CVSS scores

7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C
7.8Microsoft CorporationCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-59Improper Link Resolution Before File Access ('Link Following')
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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