CWE-538 Base Draft

Insertion of Sensitive Information into Externally-Accessible File or Directory

This vulnerability occurs when an application unintentionally stores confidential data—like passwords, API keys, or personal user details—in a location that is publicly accessible or readable by…

Definition

What is CWE-538?

This vulnerability occurs when an application unintentionally stores confidential data—like passwords, API keys, or personal user details—in a location that is publicly accessible or readable by unauthorized users. Even if the file itself is intended to be available, the sensitive information within it should not be.
This flaw typically happens due to misconfigured file permissions, insecure default settings, or development practices that accidentally write secrets into log files, debug dumps, configuration files, or temporary directories. For example, an application might log full HTTP requests containing session tokens, or a deployment script could leave a backup file with database credentials in a web-accessible folder. Attackers can easily discover and exploit these exposed files using automated scanners or by guessing common file names. To prevent this, developers should implement strict access controls, ensuring sensitive files are stored outside web roots with proper permissions. Application code must avoid logging secrets, and automated processes should scrub sensitive data from any output. Regular security scans of publicly accessible directories are essential to detect accidental information leaks before they can be exploited.
Real-world impact

Real-world CVEs caused by CWE-538

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 Java

In the following code snippet, a user's full name and credit card number are written to a log file.

Vulnerable Java 
logger.info("Username: " + usernme + ", CCN: " + ccn);
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-538

  • Architecture and Design / Operation / System Configuration Do not expose file and directory information to the user.
Detection signals

How to detect CWE-538

Automated Static Analysis High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Plexicus auto-fix

Plexicus auto-detects CWE-538 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-538?

This vulnerability occurs when an application unintentionally stores confidential data—like passwords, API keys, or personal user details—in a location that is publicly accessible or readable by unauthorized users. Even if the file itself is intended to be available, the sensitive information within it should not be.

How serious is CWE-538?

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-538?

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

How can I prevent CWE-538?

Do not expose file and directory information to the user.

How does Plexicus detect and fix CWE-538?

Plexicus's SAST engine matches the data-flow signature for CWE-538 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-538?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/538.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-538

CWE-200 Parent

Exposure of Sensitive Information to an Unauthorized Actor

This weakness occurs when an application unintentionally reveals sensitive data to someone who shouldn't have access to it.

CWE-1258 Sibling

Exposure of Sensitive System Information Due to Uncleared Debug Information

This vulnerability occurs when hardware fails to erase sensitive data like cryptographic keys and intermediate values before entering…

CWE-1273 Sibling

Device Unlock Credential Sharing

This vulnerability occurs when the secret keys or passwords required to unlock a device's hidden features are shared between multiple…

CWE-1295 Sibling

Debug Messages Revealing Unnecessary Information

The product's debug messages or logs expose excessive internal system details, potentially revealing sensitive information that could aid…

CWE-1431 Sibling

Driving Intermediate Cryptographic State/Results to Hardware Module Outputs

This vulnerability occurs when a hardware cryptographic module leaks sensitive internal data through its output channels. Instead of only…

CWE-201 Sibling

Insertion of Sensitive Information Into Sent Data

This vulnerability occurs when an application sends data to an external party, but accidentally includes sensitive information—like…

CWE-203 Sibling

Observable Discrepancy

This vulnerability occurs when an application responds differently to unauthorized users based on internal conditions. Attackers can…

CWE-209 Sibling

Generation of Error Message Containing Sensitive Information

This vulnerability occurs when an application reveals sensitive details about its internal systems, user data, or environment within error…

CWE-213 Sibling

Exposure of Sensitive Information Due to Incompatible Policies

This vulnerability occurs when a system's data handling aligns with the developer's security rules but accidentally reveals information…

Resources

Further reading

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