+44 1865 950 828 Secure Your Business
Actively exploitedKnown ransomware use

CVE-2021-27104 Accellion FTA OS Command Injection Vulnerability

Accellion FTA contains an OS command injection vulnerability exploited via a crafted POST request to various admin endpoints.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 3 Nov 2021.
  • CISA lists it as known to be used in ransomware campaigns.
  • Rated Critical severity (CVSS 9.8, scored by CISA).
  • It has been in the catalogue for 1,829 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

Accellion FTA 9_12_370 and earlier is affected by OS command execution via a crafted POST request to various admin endpoints. The fixed version is FTA_9_12_380 and later.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Accellion FTA. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated critical, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 17 Nov 2021 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Accellion Flaws

Get alerts for AccellionWe email you when a new Accellion vulnerability is confirmed as exploited. Add more vendors on Threat Watch.

By signing up you agree to receive Threat Watch alerts. Unsubscribe at any time. See our Privacy Policy.

CVE-2021-27102 · RansomwareAccellion FTA OS Command Injection VulnerabilityAdded 3 Nov 2021CVE-2021-27101 · RansomwareAccellion FTA SQL Injection VulnerabilityAdded 3 Nov 2021CVE-2021-27103 · RansomwareAccellion FTA Server-Side Request Forgery (SSRF) VulnerabilityAdded 3 Nov 2021

All 4 exploited Accellion vulnerabilities

Not Sure If You Are Exposed?

Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2021-27104 and every other exploited flaw on the list.

Check My Exposure
Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2021-27104
  3. CVE record: CVE-2021-27104
  4. FIRST EPSS
  5. accellion.com/products/fta/
  6. github.com/accellion/CVEs/blob/main/CVE-2021-27104.txt