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PatchSiren cyber security CVE debrief

CVE-2021-27104 Accellion CVE debrief

CVE-2021-27104 affects Accellion FTA and is identified by CISA as a known exploited vulnerability. Because it was added to the Known Exploited Vulnerabilities catalog and associated with ransomware campaign use, organizations running FTA should treat it as a high-priority remediation item.

Vendor
Accellion
Product
FTA
CVSS
Unknown
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, system administrators, and incident responders responsible for Accellion FTA deployments, especially any organization with exposed or still-operational instances.

Technical summary

Official vulnerability and KEV records describe CVE-2021-27104 as an OS command injection issue in Accellion FTA. CISA lists it as known exploited, with known ransomware campaign use, indicating active abuse rather than a purely theoretical flaw.

Defensive priority

Critical

Recommended defensive actions

  • Apply updates per vendor instructions as directed by CISA KEV guidance.
  • Inventory and locate any Accellion FTA instances, including legacy or forgotten deployments.
  • Prioritize remediation of exposed systems before lower-risk maintenance work.
  • Review affected systems for signs of compromise and follow incident response procedures if suspicious activity is found.
  • Verify that monitoring, logging, and asset tracking cover any remaining FTA systems.

Evidence notes

This debrief is based on the supplied CISA Known Exploited Vulnerabilities metadata for CVE-2021-27104, which lists Accellion FTA, date added 2021-11-03, due date 2021-11-17, required action to apply updates per vendor instructions, and known ransomware campaign use. Official CVE and NVD records are provided as reference links.

Sources and references

Verified primary and authoritative sources

  • CVE-2021-27104 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2021-27104

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

  • CVE-2021-27104 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2021-27104

    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.