CVE-2021-36934

CVE-2021-36934 is a high-severity vulnerability in Microsoft Windows 10 1809 with a CVSS 3.x base score of 7.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2022-02-10).

Key facts

• Severity: High (CVSS 3.x base score 7.8)
• CVSS v2: 4.6
• EPSS exploit prediction: 67% (99th percentile)
• Actively exploited: Yes — listed in CISA KEV (added 2022-02-10)
• EU (EUVD) id: EUVD-2021-23510
• EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2022-02-10)
• Affected product: Microsoft Windows 10 1809
• Published: 2021-07-22
• Last modified: 2026-06-17

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>

Frequently asked questions

What is CVE-2021-36934?

<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>

How severe is CVE-2021-36934?

CVE-2021-36934 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-36934 being actively exploited?

Yes. CVE-2021-36934 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2022-02-10, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2021-36934?

CVE-2021-36934 primarily affects Microsoft Windows 10 1809. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-36934?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2021-36934 have an EU (EUVD) identifier?

Yes. CVE-2021-36934 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-23510. It is also flagged as exploited in the EUVD (since 2022-02-10).

When was CVE-2021-36934 published?

CVE-2021-36934 was published on 2021-07-22 and last updated on 2026-06-17.

References

• http://packetstormsecurity.com/files/164006/HiveNightmare-AKA-SeriousSAM.html
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-36934
• https://www.kb.cert.org/vuls/id/506989
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36934

Affected products (5)

• cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_10_1909:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_10_2004:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_10_20h2:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_10_21h1:*:*:*:*:*:*:*:*

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