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CVE-2021-36934

Microsoft Windows SAM Local Privilege Escalation

7.8 HIGHActively exploited (CISA KEV)EPSS 67.3%
  1. Published22 Jul 2021
  2. Added to CISA KEV10 Feb 2022
  3. Remediation due24 Feb 2022
Actively exploited (CISA KEV)

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.

Added to KEV: 10 Feb 2022Federal remediation due: 24 Feb 2022

Description

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. An attacker must have the ability to execute code on a victim system to exploit this vulnerability. After installing this security update, you must manually delete all shadow copies of system files, including the SAM database, to fully mitigate this vulnerabilty. Simply installing this security update will not fully mitigate this vulnerability. See KB5005357- Delete Volume Shadow Copies.

CVSS 3.1 breakdown

Attack vectorLocal
Attack complexityLow
Privileges requiredLow
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

Microsoft Windows 10 1809< 10.0.17763.2114
Microsoft Windows 10 1909< 10.0.18363.1734
Microsoft Windows 10 2004< 10.0.19041.1165
Microsoft Windows 10 20h2< 10.0.19042.1165
Microsoft Windows 10 21h1< 10.0.19043.1165

Remediation

Fixed in
Microsoft Windows 10 1809≥ 10.0.17763.2114
Microsoft Windows 10 1909≥ 10.0.18363.1734
Microsoft Windows 10 2004≥ 10.0.19041.1165
Microsoft Windows 10 20h2≥ 10.0.19042.1165
Microsoft Windows 10 21h1≥ 10.0.19043.1165

References

Frequently asked

Is CVE-2021-36934 being actively exploited?

Yes. CVE-2021-36934 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 10 Feb 2022.

How severe is CVE-2021-36934?

CVE-2021-36934 has a CVSS 3.1 base score of 7.8, rated high. EPSS estimates a 67.3% probability of exploitation.

Which products are affected by CVE-2021-36934?

Affected products include Microsoft Windows 10 1809, Microsoft Windows 10 1909, Microsoft Windows 10 2004, Microsoft Windows 10 20h2, Microsoft Windows 10 21h1.

How do I fix CVE-2021-36934?

Upgrade affected software to a fixed version, for example Microsoft Windows 10 1809 10.0.17763.2114, Microsoft Windows 10 1909 10.0.18363.1734, Microsoft Windows 10 2004 10.0.19041.1165 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-36934 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.