CWE-526 Variant Incomplete

Cleartext Storage of Sensitive Information in an Environment Variable

This vulnerability occurs when an application stores sensitive data, such as passwords or API keys, as plain text in an environment variable.

Definition

What is CWE-526?

This vulnerability occurs when an application stores sensitive data, such as passwords or API keys, as plain text in an environment variable.
Storing secrets in plain text within environment variables creates a broad attack surface. Many other processes within the same execution context can access these values, including child processes spawned by your application, third-party dependencies, and adjacent functions in serverless cloud environments. Since these components often don't actually need the secret, this practice unnecessarily exposes it. Furthermore, environment variable data can easily leak into unintended locations. Application code or logging libraries might inadvertently include these values in error messages, HTTP headers, debug outputs, or log files. This indirect exposure means that even if you don't directly read the variable in your core logic, a separate weakness elsewhere in your application stack could still disclose it.
Real-world impact

Real-world CVEs caused by CWE-526

  • CVE-2022-43691

    CMS shows sensitive server-side information from environment variables when run in Debug mode.

  • CVE-2022-27195

    Plugin for an automation server inserts environment variable contents into build XML files.

  • CVE-2022-25264

    CI/CD tool logs environment variables related to passwords add Contribution to content history.

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-526

  • Architecture and Design Encrypt information stored in the environment variable to protect it from being exposed to an unauthorized user. If encryption is not feasible or is considered too expensive for the business use of the application, then consider using a properly protected configuration file instead of an environment variable. It should be understood that unencrypted information in a config file is also not guaranteed to be protected, but it is still a better choice, because it reduces attack surface related to weaknesses such as CWE-214. In some settings, vaults might be a feasible option for safer data transfer. Users should be notified of the business choice made to not protect the sensitive information through encryption.
  • Implementation If the environment variable is not necessary for the desired behavior, then remove it entirely, or clear it to an empty value.
Detection signals

How to detect CWE-526

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

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Frequently asked questions

Frequently asked questions

What is CWE-526?

This vulnerability occurs when an application stores sensitive data, such as passwords or API keys, as plain text in an environment variable.

How serious is CWE-526?

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-526?

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

How can I prevent CWE-526?

Encrypt information stored in the environment variable to protect it from being exposed to an unauthorized user. If encryption is not feasible or is considered too expensive for the business use of the application, then consider using a properly protected configuration file instead of an environment variable. It should be understood that unencrypted information in a config file is also not guaranteed to be protected, but it is still a better choice, because it reduces attack surface related to…

How does Plexicus detect and fix CWE-526?

Plexicus's SAST engine matches the data-flow signature for CWE-526 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-526?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/526.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-526

CWE-312 Parent

Cleartext Storage of Sensitive Information

This vulnerability occurs when an application stores sensitive data like passwords, credit card numbers, or personal information in plain…

CWE-313 Sibling

Cleartext Storage in a File or on Disk

This vulnerability occurs when an application writes sensitive data, such as passwords or personal information, directly to a file or disk…

CWE-314 Sibling

Cleartext Storage in the Registry

This vulnerability occurs when an application saves sensitive data, like passwords or keys, as plain text in the Windows Registry.

CWE-315 Sibling

Cleartext Storage of Sensitive Information in a Cookie

This vulnerability occurs when an application directly stores sensitive data, like session tokens or personal details, in a browser cookie…

CWE-316 Sibling

Cleartext Storage of Sensitive Information in Memory

This vulnerability occurs when an application stores sensitive data, such as passwords or encryption keys, in memory without any form of…

CWE-317 Sibling

Cleartext Storage of Sensitive Information in GUI

This vulnerability occurs when an application stores sensitive data, such as passwords or personal information, in plain text within its…

CWE-318 Sibling

Cleartext Storage of Sensitive Information in Executable

This vulnerability occurs when an application embeds sensitive information, like passwords or keys, directly within its executable code…

CWE-214 Peer

Invocation of Process Using Visible Sensitive Information

This vulnerability occurs when a process is started with sensitive data, such as passwords or API keys, passed directly in its…

Resources

Further reading

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