Very High
CVE-2021-36934 Windows Elevation of Privilege
CVE-2021-36934 Windows Elevation of Privilege
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.
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Technical Analysis
Vulnerability is easy to exploit – by interacting with the local ShadowCopy volume, and copying it to a local folder, attackers can easily elevate their privileges.
Several exploits were already released, allowing to parse the hashes while copying the SAM\SECURITY\SYSTEM hives:
https://github.com/cube0x0/CVE-2021-36934
https://github.com/HuskyHacks/ShadowSteal
This vulnerability occurs due to the permissive “C:\Windows\System32\Config*.*” privileges, “BUILTIN\Users”, allowing any user to read and execute the files.
Technical Analysis
Zero-day LPE vulnerability affecting Windows 10 v1809 and later (so Win10 and Win11 preview), arises from SAM file’s being READ-enabled for all local users. SAM file has gold, e.g., hashed user/admin passwords. PoC to retrieve registry hives publicly available, no patch as of July 21, 2021. JonasLyk and research community reported and confirmed the issue on Twitter Monday, July 19. Guidance from Microsoft is to apply a couple of workarounds—defenders likely behind the attack curve already. Details: https://www.rapid7.com/blog/post/2021/07/21/microsoft-sam-file-readability-cve-2021-36934-what-you-need-to-know/
CVSS V3 Severity and Metrics
General Information
Vendors
- microsoft
Products
- windows 10 1809,
- windows 10 1909,
- windows 10 2004,
- windows 10 20h2,
- windows 10 21h1
Metasploit Modules
Exploited in the Wild
