CVE-2021-36942
Windows LSA Spoofing Vulnerability
- CVSS
- 7.5Highscored by the publisher (CNA)
- Exploited in the wild
- Yes, in CISA KEV since 3 Nov 2021CISA deadline for US federal agencies: 17 Nov 2021known use in ransomware campaigns
- EPSS
- 66.0%chance of exploitation in the next 30 daystop 0.8% of scored CVEsFIRST score of 11 Nov 2026
- Fix
- Patch availablesee the advisories in the references
- Published
- 12 Aug 2021analysed here 12 Nov 2026
Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)
Summary
Triage
- Exploitable
- At runtime
- Attack vector
- network
- Can a WAF block it?
- Partly. See why
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| Microsoft Windows Server 2008 R2 Service Pack 1 | >= 6.1.7601.0 and < 6.1.7601.25685Vendor says fixed in: not stated | |
| Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) | >= 6.1.7601.0 and < 6.1.7601.25685Vendor says fixed in: not stated | |
| Microsoft Windows Server 2008 Service Pack 2 | >= 6.0.6003.0 and < 6.0.6003.21192Vendor says fixed in: not stated | |
| Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) | >= 6.0.6003.0 and < 6.0.6003.21192Vendor says fixed in: not stated | |
| Microsoft Windows Server 2012 | >= 6.2.9200.0 and < 6.2.9200.23435Vendor says fixed in: not stated | |
| Microsoft Windows Server 2012 R2 | >= 6.3.9600.0 and < 6.3.9600.20094Vendor says fixed in: not stated | |
| Microsoft Windows Server 2012 R2 (Server Core installation) | >= 6.3.9600.0 and < 6.3.9600.20094Vendor says fixed in: not stated | |
| Microsoft Windows Server 2012 (Server Core installation) | >= 6.2.9200.0 and < 6.2.9200.23435Vendor says fixed in: not stated | |
| Microsoft Windows Server 2016 | >= 10.0.14393.0 and < 10.0.14393.4583Vendor says fixed in: not stated | |
| Microsoft Windows Server 2016 (Server Core installation) | >= 10.0.14393.0 and < 10.0.14393.4583Vendor says fixed in: not stated | |
| Microsoft Windows Server 2019 | >= 10.0.17763.0 and < 10.0.17763.2114Vendor says fixed in: not stated | |
| Microsoft Windows Server 2019 (Server Core installation) | >= 10.0.17763.0 and < 10.0.17763.2114Vendor says fixed in: not stated | |
| Microsoft Windows Server version 2004 | >= 10.0.0 and < 10.0.19041.1165Vendor says fixed in: not stated | |
| Microsoft Windows Server version 20H2 | >= 10.0.0 and < 10.0.19042.1165Vendor says fixed in: not stated |
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
Products named in our analysis
- microsoft:windows_server_2004
- microsoft:windows_server_2008
- microsoft:windows_server_2012
- microsoft:windows_server_2016
- microsoft:windows_server_2019
- microsoft:windows_server_20h2
Fix and mitigation
WAF and other mitigations
Can a WAF block it? Partly. The bug can be reached over the network, so generic WAF rules may stop some attacks. Its weakness type is unknown, so we cannot be more precise.
Also consider: patch
Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Listed since 3 Nov 2021. Known use in ransomware campaigns.
- CISA due date
- 17 Nov 2021, the remediation deadline for US federal agencies
- CISA required action
- Apply updates per vendor instructions.
- Public exploit code
- Detection templates only, no public exploit found: 1 Metasploit module
- CISA SSVC
- exploitation active, automatable yes, technical impact totalAssessed by CISA 4 Feb 2025 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
Metasploit
- auxiliary/scanner/dcerpc/petitpotamauxiliary, rank normal
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
Timeline
- 12 Aug 2021Published
- 3 Nov 2021Added to CISA KEV (exploited in the wild)82 days (about 3 months) later
- 17 Nov 2021CISA remediation due date (US federal agencies)14 days later
- 4 Feb 2025CISA SSVC assessment: exploitation active1,176 days (about 3 years) later
- 10 Aug 2026CVE record last updated552 days (about 2 years) later
- 12 Nov 2026Analysed by vulneraibility.com94 days (about 3 months) later
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
| Metric | Value | What it means |
|---|---|---|
| Attack vector | NetworkReachable over the internet or any routable network. | Reachable over the internet or any routable network. |
| Attack complexity | LowRepeatable attack, no special conditions. | Repeatable attack, no special conditions. |
| Privileges required | NoneThe attacker needs no prior access. | The attacker needs no prior access. |
| User interaction | NoneNo victim action needed. | No victim action needed. |
| Scope | UnchangedImpact stays within the vulnerable component. | Impact stays within the vulnerable component. |
| Confidentiality | HighTotal data disclosure possible. | Total data disclosure possible. |
| Integrity | NoneNo unauthorised modification. | No unauthorised modification. |
| Availability | NoneThe service stays up. | The service stays up. |
Common questions
Is CVE-2021-36942 being exploited?
Yes. CVE-2021-36942 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2021-36942?
CVE-2021-36942 is rated High with a CVSS score of 7.5. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2021-36942?
Yes. A fix has been recorded for CVE-2021-36942. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2021-36942 affect?
CVE-2021-36942 affects microsoft:windows_server_2004, microsoft:windows_server_2008, microsoft:windows_server_2012, microsoft:windows_server_2016, and 2 further products or versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
References
4 references in the CVE record, grouped by the tags the record gives them.
Advisories (1)
- kb.cert.org /vuls/id/405600
Patches (1)
- msrc.microsoft.com /update-guide/vulnerability/CVE-2021-36942
Other links (2)
- portal.msrc.microsoft.com /en-US/security-guidance/advisory/CVE-2021-36942
- cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36942
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Metasploit Framework: exploit and scanner modules
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
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