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PatchSiren cyber security CVE debrief

CVE-2021-27085 Microsoft CVE debrief

CVE-2021-27085 is a Microsoft Internet Explorer remote code execution vulnerability. In the supplied source corpus, CISA listed it in the Known Exploited Vulnerabilities catalog on 2021-11-03, indicating known exploitation and making remediation time-sensitive. CISA’s due date for applying updates was 2021-11-17.

Vendor
Microsoft
Product
Internet Explorer
CVSS
HIGH 8.8
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

Security teams responsible for Microsoft endpoints, patch management, and any environment where Internet Explorer is still enabled or reachable. This is especially important for organizations that track CISA KEV items as urgent remediation priorities.

Technical summary

The supplied corpus identifies CVE-2021-27085 as a Microsoft Internet Explorer remote code execution vulnerability. No further technical details, exploit conditions, or affected-version breakdown are provided in the supplied sources. The key operational signal is that CISA added it to the Known Exploited Vulnerabilities catalog on 2021-11-03 and set a remediation due date of 2021-11-17.

Defensive priority

Urgent

Recommended defensive actions

  • Apply Microsoft updates per vendor instructions as soon as possible.
  • Prioritize any systems where Internet Explorer remains enabled or in use.
  • Validate patch deployment against the CISA KEV due date of 2021-11-17 or sooner.
  • Review endpoint and browser telemetry for signs of suspicious activity on affected systems.
  • If Internet Explorer is not required, reduce exposure by disabling or restricting its use where your environment allows it.

Evidence notes

Supported facts from the supplied corpus: Microsoft is the vendor; the product is Internet Explorer; the vulnerability is described as a remote code execution issue; CISA classified it as a known exploited vulnerability; dateAdded is 2021-11-03; dueDate is 2021-11-17; knownRansomwareCampaignUse is Unknown. No CVSS score or detailed exploitation mechanics were provided in the corpus.

Sources and references

Verified primary and authoritative sources

  • CVE-2021-27085 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2021-27085

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

  • CVE-2021-27085 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2021-27085

    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.