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CVE-2021-36934

Windows Elevation of Privilege Vulnerability

HIGH
7.8
CVSS Score
Published: July 22, 2021 at 07:05 AM UTC
Updated: August 10, 2026 at 08:38 PM UTC
5 products affected across 1 vendorWindows 10 1809Windows 10 1909Windows 10 20H2

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Severity
HIGH7.8
Exploitation
CISA KEV
Exploit prediction
EPSS 67%
SSVC
Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score67.3%

EPSS (Exploit Prediction Scoring System) estimates a 67.3% chance this CVE is exploited in the wild within the next 30 days — higher than 99% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

If a Volume Shadow Copy (VSS) shadow copy of the system drive is available, users can read the SAM file which would allow any user to escalate privileges to SYSTEM level.

Required Action
Apply updates per vendor instructions.
Ransomware Use
Unknown
Added to KEV
Feb 10, 2022
Remediation Due
Feb 24, 2022
1710 days overdue
Notes
https://nvd.nist.gov/vuln/detail/CVE-2021-36934

Description

<p>An elevation of privilege vulnerability exists because of overly permissive Access Control Lists (ACLs) on multiple system files, including the Security Accounts Manager (SAM) database. An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.</p> <p>An attacker must have the ability to execute code on a victim system to exploit this vulnerability.</p> <p>After installing this security update, you <em>must</em> manually delete all shadow copies of system files, including the SAM database, to fully mitigate this vulnerabilty. <strong>Simply installing this security update will not fully mitigate this vulnerability.</strong> See <a href="https://support.microsoft.com/topic/1ceaa637-aaa3-4b58-a48b-baf72a2fa9e7">KB5005357- Delete Volume Shadow Copies</a>.</p>

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Windows 10 1809· Microsoft
95%
v < 10.0.17763.211410.0.0 ≤ v < 10.0.17763.211410.0.0 ≤ v < 10.0.19041.116510.0.17763.0 ≤ v < 10.0.17763.211410.0.010.0.17763.0
Affected range stops below 10.0.17763.2114, so it looks safe — our inference, not a vendor statement
Affected range stops below 10.0.19041.1165, so it looks safe — our inference, not a vendor statement
Windows 10 1909· Microsoft
95%
v < 10.0.18363.173410.0.0 ≤ v < 10.0.18363.173410.0.0
Affected range stops below 10.0.18363.1734, so it looks safe — our inference, not a vendor statement
Windows 10 2004· Microsoft
95%
v < 10.0.19041.116510.0.0 ≤ v < 10.0.19041.116510.0.0
Affected range stops below 10.0.19041.1165, so it looks safe — our inference, not a vendor statement
Windows 10 20H2· Microsoft
95%
v < 10.0.19042.116510.0.0 ≤ v < 10.0.19042.116510.0.0
Affected range stops below 10.0.19042.1165, so it looks safe — our inference, not a vendor statement
Windows 10 21H1· Microsoft
95%
v < 10.0.19043.116510.0.0 ≤ v < 10.0.19043.116510.0.0
Affected range stops below 10.0.19043.1165, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (5)

Third Party AdvisoryVDB Entry
Source: [email protected]
http://packetstormsecurity.com/files/164006/HiveNightmare-AKA-SeriousSAM.html
PatchVendor Advisory
Source: [email protected]
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-36934
Third Party Advisory
Source: af854a3a-2127-422b-91ae-364da2661108
https://www.kb.cert.org/vuls/id/506989
Vendor AdvisoryPatch
Source: cverecord
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36934
US Government Resource
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36934

SSVC — Action Prioritization

SSVCActiveNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.8HIGHmicrosoft
Vector?

Quick Info

StatusANALYZED
CWE
NVD-CWE-Other

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