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PatchSiren cyber security CVE debrief

CVE-2021-36942 Microsoft CVE debrief

CVE-2021-36942 is a Microsoft Windows Local Security Authority (LSA) spoofing vulnerability that CISA added to its Known Exploited Vulnerabilities catalog on 2021-11-03. CISA also marks it as associated with known ransomware campaign use, so this should be treated as a high-priority patching item for Windows environments.

Vendor
Microsoft
Product
Windows
CVSS
HIGH 7.5
CISA KEV
Listed
Original CVE published
2021-11-03
Original CVE updated
2021-11-03
Advisory published
2021-11-03
Advisory updated
2021-11-03

Who should care

Windows administrators, endpoint and server security teams, vulnerability management programs, and incident responders should prioritize this CVE, especially where Windows systems are broadly deployed or exposed to higher-risk user activity.

Technical summary

The publicly available record identifies this issue as a Microsoft Windows Local Security Authority (LSA) spoofing vulnerability. The supplied corpus does not include deeper technical details or a CVSS score, but it does confirm the vulnerability was listed in CISA's KEV catalog and associated with known exploitation activity.

Defensive priority

Urgent

Recommended defensive actions

  • Apply Microsoft updates per vendor instructions as soon as possible.
  • Prioritize remediation on internet-facing, high-value, and heavily used Windows systems.
  • Confirm asset inventory coverage so all affected Windows endpoints and servers are included in patching.
  • Validate that remediation completed successfully across the fleet.
  • Monitor for suspicious authentication-related activity and investigate any signs of compromise in Windows environments.

Evidence notes

The source corpus confirms: Microsoft as vendor, Windows as the product, and the vulnerability name 'Microsoft Windows Local Security Authority (LSA) Spoofing Vulnerability.' CISA KEV lists the item with dateAdded 2021-11-03, dueDate 2021-11-17, requiredAction 'Apply updates per vendor instructions,' and knownRansomwareCampaignUse 'Known.' No CVSS score was provided in the supplied data.

Sources and references

Verified primary and authoritative sources

  • CVE-2021-36942 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2021-36942

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2021-36942 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2021-36942

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

  • CISA Known Exploited Vulnerabilities catalog

    Publisher, destination, and source semantics verified

    URL: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

    Cybersecurity and Infrastructure Security Agency - Official CISA catalog of vulnerabilities known to be exploited in the wild.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

    cisa_kev

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.