CVE-2021-36934

CVE-2021-36934 is a high-severity (CVSS 7.8) vulnerability in Microsoft Windows. CISA added it to the Known Exploited Vulnerabilities catalog on February 10, 2022, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by February 24, 2022. CISA does not currently list it as used in ransomware campaigns. Microsoft has 390 vulnerabilities in the KEV catalog, 117 of them linked to ransomware.

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 vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36934
• 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