Microsoft Windows Local Security Authority (LSA) Spoofing
CVE-2021-36942 is a high-severity vulnerability in Windows Server 2008 R2 Service Pack 1 from Microsoft, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 6.1.7601.25685 as the first without the flaw, so updating Windows Server 2008 R2 Service Pack 1 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild, including in ransomware campaigns.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Windows Server 2008 R2 Service Pack 1 to 6.1.7601.25685 or a later version.
- Update Windows Server 2008 R2 Service Pack 1 (Server Core installation) to 6.1.7601.25685 or a later version.
- Update Windows Server 2008 Service Pack 2 to 6.0.6003.21192 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Windows Server 2008 R2 Service Pack 1 | 6.1.7601.0 up to, but not including, 6.1.7601.25685 | 6.1.7601.25685 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 (Server Core installation) | 6.1.7601.0 up to, but not including, 6.1.7601.25685 | 6.1.7601.25685 |
| Microsoft | Windows Server 2008 Service Pack 2 | 6.0.6003.0 up to, but not including, 6.0.6003.21192 | 6.0.6003.21192 |
| Microsoft | Windows Server 2008 Service Pack 2 (Server Core installation) | 6.0.6003.0 up to, but not including, 6.0.6003.21192 | 6.0.6003.21192 |
| Microsoft | Windows Server 2012 | 6.2.9200.0 up to, but not including, 6.2.9200.23435 | 6.2.9200.23435 |
| Microsoft | Windows Server 2012 (Server Core installation) | 6.2.9200.0 up to, but not including, 6.2.9200.23435 | 6.2.9200.23435 |
| Microsoft | Windows Server 2012 R2 | 6.3.9600.0 up to, but not including, 6.3.9600.20094 | 6.3.9600.20094 |
| Microsoft | Windows Server 2012 R2 (Server Core installation) | 6.3.9600.0 up to, but not including, 6.3.9600.20094 | 6.3.9600.20094 |
| Microsoft | Windows Server 2016 | 10.0.14393.0 up to, but not including, 10.0.14393.4583 | 10.0.14393.4583 |
| Microsoft | Windows Server 2016 (Server Core installation) | 10.0.14393.0 up to, but not including, 10.0.14393.4583 | 10.0.14393.4583 |
| Microsoft | Windows Server 2019 | 10.0.17763.0 up to, but not including, 10.0.17763.2114 | 10.0.17763.2114 |
| Microsoft | Windows Server 2019 (Server Core installation) | 10.0.17763.0 up to, but not including, 10.0.17763.2114 | 10.0.17763.2114 |
| Microsoft | Windows Server version 2004 | 10.0.0 up to, but not including, 10.0.19041.1165 | 10.0.19041.1165 |
| Microsoft | Windows Server version 20H2 | 10.0.0 up to, but not including, 10.0.19042.1165 | 10.0.19042.1165 |
| Microsoft | Windows Server 2004 | before 10.0.19041.1165 | 10.0.19041.1165 |
| Microsoft | Windows Server 2008 | r2 | Not stated |
| Microsoft | Windows Server 20h2 | before 10.0.19042.1165 | 10.0.19042.1165 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.5 | High | CNA (microsoft.com) |
| CVSS 3.1 | 7.5 | High | NVD |
| CVSS 2.0 | 5.0 | Medium | NVD |
Official description
Windows LSA Spoofing Vulnerability
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36942US Government Resource
Technical write-ups (may include proof of concept)
- kb.cert.org/vuls/id/405600Exploit, Third Party Advisory, US Government Resource
Other vulnerabilities in Windows Server 2008 R2 Service Pack 1
- 7.5 High severity
- 7.5 High severity
- 7.0 High severity
- 7.8 High severity
- 7.0 High severity
- 7.8 High severity
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