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PatchSiren cyber security CVE debrief

CVE-2021-31956 Microsoft CVE debrief

CVE-2021-31956 is a Microsoft Windows NTFS privilege escalation vulnerability that CISA included in its Known Exploited Vulnerabilities catalog on 2021-11-03. Because CISA lists it as known exploited, defenders should treat it as a high-priority patching and exposure-reduction item and follow vendor update guidance without delay.

Vendor
Microsoft
Product
Windows
CVSS
HIGH 7.8
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 vulnerability management teams, security operations, and incident response teams should prioritize this CVE because it is listed in CISA’s Known Exploited Vulnerabilities catalog.

Technical summary

The supplied official records identify the issue as a Microsoft Windows NTFS privilege escalation vulnerability. The available corpus does not provide deeper technical details such as the affected Windows versions, exploit prerequisites, or attack vector. The key defensive signal is CISA’s KEV listing, which indicates known exploitation and a required response of applying updates per vendor instructions.

Defensive priority

Urgent. CISA added CVE-2021-31956 to the Known Exploited Vulnerabilities catalog, which signals active exploitation risk and makes timely remediation a priority for Windows environments.

Recommended defensive actions

  • Apply Microsoft updates per vendor instructions as soon as possible.
  • Verify whether any Windows systems in your environment are exposed to the NTFS component implicated by this CVE.
  • Prioritize remediation in internet-facing, privileged, and high-value endpoints first.
  • Use vulnerability management and patch compliance reporting to confirm closure across the fleet.
  • Monitor for any signs of suspicious privilege escalation activity while remediation is underway.

Evidence notes

This debrief is based on the supplied CISA KEV source item and official record links only. The corpus confirms the CVE ID, Microsoft Windows NTFS privilege escalation title, CISA KEV inclusion, dateAdded 2021-11-03, dueDate 2021-11-17, and the required action to apply updates per vendor instructions. No additional technical exploitation details were present in the provided source corpus, so none are asserted here.

Sources and references

Verified primary and authoritative sources

  • CVE-2021-31956 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2021-31956

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

  • CVE-2021-31956 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2021-31956

    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.