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PatchSiren cyber security CVE debrief

CVE-2021-27059 Microsoft CVE debrief

CVE-2021-27059 is a Microsoft Office remote code execution vulnerability that CISA added to its Known Exploited Vulnerabilities catalog on 2021-11-03. The CISA entry indicates this issue was actively exploited and required prompt remediation. The supplied source corpus does not include technical exploit details or affected-version specifics, so the safest response is to treat all relevant Microsoft Office deployments as high priority for vendor-guided updating.

Vendor
Microsoft
Product
Office
CVSS
HIGH 7.6
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

Security teams, IT administrators, endpoint management teams, and Microsoft Office owners should care, especially if they manage large Office deployments or have limited patch visibility.

Technical summary

The official material provided identifies the issue as a Microsoft Office remote code execution vulnerability and marks it as a CISA KEV item. Beyond that, the corpus does not provide attack preconditions, impacted builds, or CVSS data. The key operational takeaway is that CISA has treated it as known exploited, so remediation should follow Microsoft’s update guidance and be prioritized accordingly.

Defensive priority

High. CISA KEV inclusion signals known exploitation and a tight remediation deadline (2021-11-17 in the supplied timeline).

Recommended defensive actions

  • Apply Microsoft’s vendor-recommended updates for affected Office installations as soon as possible.
  • Prioritize affected assets against the CISA KEV due date of 2021-11-17.
  • Inventory Microsoft Office deployments to identify exposed endpoints and missing patches.
  • Verify patch status after remediation and include the CVE in vulnerability management tracking.
  • Monitor Microsoft, CISA, and NVD pages for any updated guidance or scope clarification.

Evidence notes

This debrief is based only on the supplied official sources: the CISA Known Exploited Vulnerabilities catalog entry, the CVE record, and the NVD detail page reference. The corpus confirms the CVE ID, product family (Microsoft Office), vulnerability class (remote code execution), KEV status, date added (2021-11-03), and due date (2021-11-17). No CVSS score, affected version list, or exploit mechanics were provided in the source corpus, so those details are intentionally omitted.

Sources and references

Verified primary and authoritative sources

  • CVE-2021-27059 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2021-27059

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

  • CVE-2021-27059 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2021-27059

    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.