CVE-2021-27104Known exploitationNetwork attack vector

Command execution via crafted administrative POST requests

Published Feb 16, 2021 · Updated Oct 21, 2025

OS command injection in Accellion FTA 9.12.370 and earlier allows remote attackers to execute commands through crafted POST requests. Administrative API endpoints, including sftp_account_edit.php, process attacker-controlled request data as operating-system commands without effective validation or sanitization. Observed unauthenticated attacks first forged valid API tokens through a separate SQL injection, then created a web shell that enabled stored-file exfiltration.

CVSS severity9.8
Critical
EPSS probability56.69%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in Accellion FTA 9.12.370 and earlier allows remote attackers to execute commands through crafted POST requests. Administrative API endpoints, including sftp_account_edit.php, process attacker-controlled request data as operating-system commands without effective validation or sanitization. Observed unauthenticated attacks first forged valid API tokens through a separate SQL injection, then created a web shell that enabled stored-file exfiltration.

The record

CVE
CVE-2021-27104
Published
Feb 16, 2021
Updated
Oct 21, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-20, CWE-78, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 16, 2020Exploitation reportedUNC2546 exploitation of Accellion FTA
  2. Feb 16, 2021CVE publishedPublication date reported by the CVE source.
  3. Oct 21, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

10.0TenableAV:N/AC:L/Au:N/C:C/I:C/A:C
9.8TenableCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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