CWE-220 Variant Draft

Storage of File With Sensitive Data Under FTP Root

This vulnerability occurs when an application saves sensitive files, such as configuration or user data, within the directory served by an FTP server without proper access restrictions. This…

Definition

What is CWE-220?

This vulnerability occurs when an application saves sensitive files, such as configuration or user data, within the directory served by an FTP server without proper access restrictions. This misconfiguration can allow unauthorized users to download these files directly.
FTP servers are designed to share files, so any data placed within their root directory becomes potentially accessible to anyone who can connect. If sensitive files like `.env`, backup archives, or database dumps are stored there, attackers can easily retrieve them by simply browsing or using automated tools, leading to immediate data exposure. To prevent this, developers should never use the FTP root as a general storage location for sensitive data. Instead, confidential files must be kept outside the publicly served directory tree, with strict operating system permissions and FTP server configuration ensuring that only authorized processes can access them. Regular audits of the FTP directory contents are essential to catch accidental misplacements.
Real-world impact

Real-world CVEs caused by CWE-220

No public CVE references are linked to this CWE in MITRE's catalog yet.

How attackers exploit it

Step-by-step attacker path

  1. 1

    Identify a code path that handles untrusted input without validation.

  2. 2

    Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.

  3. 3

    Deliver the payload through a normal request and observe the application's reaction.

  4. 4

    Iterate until the response leaks data, executes attacker code, or escalates privileges.

Vulnerable code example

Vulnerable pseudo

MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.

Vulnerable pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
Secure code example

Secure pseudo

Secure pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist

How to prevent CWE-220

  • Implementation / System Configuration Avoid storing information under the FTP root directory.
  • System Configuration Access control permissions should be set to prevent reading/writing of sensitive files inside/outside of the FTP directory.
Detection signals

How to detect CWE-220

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

Plexicus auto-fix

Plexicus auto-detects CWE-220 and opens a fix PR in under 60 seconds.

Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.

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Frequently asked questions

Frequently asked questions

What is CWE-220?

This vulnerability occurs when an application saves sensitive files, such as configuration or user data, within the directory served by an FTP server without proper access restrictions. This misconfiguration can allow unauthorized users to download these files directly.

How serious is CWE-220?

MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.

What languages or platforms are affected by CWE-220?

MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.

How can I prevent CWE-220?

Avoid storing information under the FTP root directory. Access control permissions should be set to prevent reading/writing of sensitive files inside/outside of the FTP directory.

How does Plexicus detect and fix CWE-220?

Plexicus's SAST engine matches the data-flow signature for CWE-220 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.

Where can I learn more about CWE-220?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/220.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-220

CWE-552 Parent

Files or Directories Accessible to External Parties

This vulnerability occurs when an application exposes files or directories to users who shouldn't have access to them.

CWE-219 Sibling

Storage of File with Sensitive Data Under Web Root

This vulnerability occurs when an application saves sensitive files, such as configuration data or private keys, inside the web server's…

CWE-527 Sibling

Exposure of Version-Control Repository to an Unauthorized Control Sphere

This vulnerability occurs when a version control repository, like Git or SVN, is accidentally placed in a location accessible to…

CWE-528 Sibling

Exposure of Core Dump File to an Unauthorized Control Sphere

This vulnerability occurs when an application creates a core dump file (a snapshot of memory at the time of a crash) and places it in a…

CWE-529 Sibling

Exposure of Access Control List Files to an Unauthorized Control Sphere

This vulnerability occurs when an application stores sensitive access control list (ACL) files in a location that is accessible to…

CWE-530 Sibling

Exposure of Backup File to an Unauthorized Control Sphere

This vulnerability occurs when backup or temporary files are stored in locations that unauthorized users can access, such as web…

CWE-539 Sibling

Use of Persistent Cookies Containing Sensitive Information

This vulnerability occurs when a web application stores sensitive data, like authentication details or personal information, within…

CWE-553 Sibling

Command Shell in Externally Accessible Directory

This vulnerability occurs when a command shell script is placed in a web-accessible directory, such as /cgi-bin/. Attackers can directly…

Resources

Further reading

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