CVE-2021-33757

published 2021-07-14

CVE-2021-33757: Windows Security Account Manager Remote Protocol Security Feature Bypass Vulnerability

Priority P2 59 critical 9.8 CVSS 3.1

AV N AC L PR N UI N S U C H I H A H

Windows Security Account Manager Remote Protocol Security Feature Bypass Vulnerability

Affected

43 ranges · showing 25

Vendor	Product	Version range	Fixed in
microsoft	windows_10	—	—
microsoft	windows_10	—	—
microsoft	windows_10	—	—
microsoft	windows_10	—	—
microsoft	windows_10	—	—
microsoft	windows_10	—	—
microsoft	windows_10_version_1507	>= 10.0.0 < 10.0.10240.19003	10.0.10240.19003
microsoft	windows_10_version_1607	>= 10.0.0 < 10.0.14393.4530	10.0.14393.4530
microsoft	windows_10_version_1809	>= 10.0.0 < 10.0.17763.2061	10.0.17763.2061
microsoft	windows_10_version_1909	>= 10.0.0 < 10.0.18363.1679	10.0.18363.1679
microsoft	windows_10_version_2004	>= 10.0.0 < 10.0.19041.1110	10.0.19041.1110
microsoft	windows_10_version_20h2	>= 10.0.0 < 10.0.19042.1110	10.0.19042.1110
microsoft	windows_10_version_21h1	>= 10.0.0 < 10.0.19043.1110	10.0.19043.1110
microsoft	windows_7	>= 6.1.0 < 6.1.7601.25661	6.1.7601.25661
microsoft	windows_7_service_pack_1	>= 6.1.0 < 6.1.7601.25661	6.1.7601.25661
microsoft	windows_8.1	>= 6.3.0 < 6.3.9600.20069	6.3.9600.20069
microsoft	windows_server_2008_r2_service_pack_1	>= 6.0.0 < 6.1.7601.25661	6.1.7601.25661
microsoft	windows_server_2008_r2_service_pack_1	>= 6.1.0 < 6.1.7601.25661	6.1.7601.25661
microsoft	windows_server_2008_service_pack_2	>= 6.0.0 < 6.0.6003.21167	6.0.6003.21167
microsoft	windows_server_2012	>= 6.2.0 < 6.2.9200.23409	6.2.9200.23409
microsoft	windows_server_2012_r2	>= 6.3.0 < 6.3.9600.20069	6.3.9600.20069
microsoft	windows_server_2016	—	—
microsoft	windows_server_2016	—	—
microsoft	windows_server_2016	>= 10.0.0 < 10.0.14393.4530	10.0.14393.4530
microsoft	windows_server_2019	>= 10.0.0 < 10.0.17763.2061	10.0.17763.2061

Detection & IOCs extracted from sources · hover to see the quote

• → Monitor for MS-SAMR protocol password change/set operations that do NOT use AES encryption (i.e., still using RC4/DES), which may indicate a downgrade attack exploiting CVE-2021-33757 ↗
• → Review Windows Event Logs for SAM-related encryption negotiation events introduced by the July 13, 2021 update; the KB5004605 update adds specific event logging for this behavior ↗
• → Audit registry settings related to MS-SAMR AES enforcement introduced by KB5004605 to detect misconfiguration or tampering that could re-enable weak encryption ↗

• · AES encryption is only preferred when the SAM server supports it; environments with unpatched SAM servers may still negotiate weak encryption even after client-side patching ↗
• · The vulnerability has not been publicly exploited or disclosed as of the advisory; exploitation is rated 'Less Likely' for both latest and older software releases ↗

CVSS provenance

nvd v3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd v2.0 7.5 HIGH AV:N/AC:L/Au:N/C:P/I:P/A:P

vendor_msrc 5.3 MEDIUM

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