cbcvebase.
CVE-2021-36934
published 2021-07-22

CVE-2021-36934: An elevation of privilege vulnerability exists because of overly permissive Access Control Lists (ACLs) on multiple system files, including the Security…

PriorityP185high7.8CVSS 3.1
AVLACLPRLUINSUCHIHAH
KEVITWEXPLOIT
CISA Known Exploited Vulnerabilitydue 2022-02-24
Exploited in the wild
EPSS
67.25%
99.2th percentile
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.

Affected

25 ranges
VendorProductVersion rangeFixed in
microsoftwindows_10_1809< 10.0.17763.211410.0.17763.2114
microsoftwindows_10_1909< 10.0.18363.173410.0.18363.1734
microsoftwindows_10_2004< 10.0.19041.116510.0.19041.1165
microsoftwindows_10_20h2< 10.0.19042.116510.0.19042.1165
microsoftwindows_10_21h1< 10.0.19043.116510.0.19043.1165
microsoftwindows_10_version_1809>= 10.0.0 < 10.0.17763.211410.0.17763.2114
microsoftwindows_10_version_1909>= 10.0.0 < 10.0.18363.173410.0.18363.1734
microsoftwindows_10_version_2004>= 10.0.0 < 10.0.19041.116510.0.19041.1165
microsoftwindows_10_version_20h2>= 10.0.0 < 10.0.19042.116510.0.19042.1165
microsoftwindows_10_version_21h1>= 10.0.0 < 10.0.19043.116510.0.19043.1165
msrcwindows_10_version_1809_for_32-bit_systems
msrcwindows_10_version_1809_for_arm64-based_systems
msrcwindows_10_version_1809_for_x64-based_systems
msrcwindows_10_version_1909_for_32-bit_systems
msrcwindows_10_version_1909_for_arm64-based_systems
msrcwindows_10_version_1909_for_x64-based_systems
msrcwindows_10_version_2004_for_32-bit_systems
msrcwindows_10_version_2004_for_arm64-based_systems
msrcwindows_10_version_2004_for_x64-based_systems
msrcwindows_10_version_20h2_for_32-bit_systems
msrcwindows_10_version_20h2_for_arm64-based_systems
msrcwindows_10_version_20h2_for_x64-based_systems
msrcwindows_10_version_21h1_for_32-bit_systems
msrcwindows_10_version_21h1_for_arm64-based_systems
msrcwindows_10_version_21h1_for_x64-based_systems

Detection & IOCsextracted from sources · hover to see the quote

hash422411a976daad538aff6a61201934b4d60372a6afe7981b2b2b684a852ef6d7
hash92e853dd359cb3636fa165a7170498d14ef7c692d8e6545b7adea95d89fe189f
hashe9cab9ddd3aa4f20aff8d33991f5996deb50bb02
hasha3bf960f6d124d0b53608ddb0c65177d3717a22f
commandicacls C:WindowsSystem32configSAM
commandvssadmin list shadows
urlhttps://github.com/romarroca/SeriousSam
urlhttps://github.com/HuskyHacks/ShadowSteal
sigma
.*?HarddiskVolumeShadowCopy[0-9]+\Windows\System32\config\SAM.*?
sigma
.*?cmd.*?mklink.*?HarddiskVolumeShadowCopy.*?
  • Monitor for any process reading files under HarddiskVolumeShadowCopy paths targeting Windows\System32\config\SAM — this is the primary exploitation pattern for CVE-2021-36934.
  • Detect symbolic link creation referencing HarddiskVolumeShadowCopy via cmd mklink, PowerShell, or fsutil.exe — used to access locked hive files from shadow copies.
  • Alert on execution of 'vssadmin list shadows' by non-administrative or unexpected processes, as attackers use this to enumerate available Volume Shadow Copies before extracting SAM/SYSTEM hives.
  • Detect use of CERTUTIL to dump SAM database contents to the TEMP folder — a key post-exploitation step in HiveNightmare attacks.
  • Check ACL permissions on C:\Windows\System32\config\SAM; if BUILTIN\Users has RX (Read+Execute) access, the system is vulnerable and may already be targeted.
  • Map detections to MITRE ATT&CK T1003.002 (Credential Dumping: SAM), T1552.001 (Credentials in Files), T1218 (Signed Binary Proxy Execution), T1202 (Indirect Command Execution), and T1012 (Query Registry) for CVE-2021-36934 activity.
  • Post-exploitation Metasploit module targets SAM and SYSTEM hive extraction via Volume Shadow Copy; once dumped to store_loot, hashes can be cracked with secretsdump.py.
  • ·Exploitation requires Volume Shadow Copies to be present on the target system; if no VSS snapshots exist, the primary attack path is blocked.
  • ·Installing the Microsoft security update alone is insufficient — shadow copies of system files including the SAM database must also be manually deleted to fully mitigate the vulnerability.
  • ·Exploitation requires the attacker to already have code execution on the victim system; this is a local privilege escalation, not a remote unauthenticated attack.

CVSS provenance

nvdv3.17.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
nvdv2.04.6MEDIUMAV:L/AC:L/Au:N/C:P/I:P/A:P
vulncheck7.8HIGH
cisa7.8HIGH
vendor_msrc7.8HIGH
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