CWE-315 Variant Draft

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 without encryption.

Definition

What is CWE-315?

This vulnerability occurs when an application directly stores sensitive data, like session tokens or personal details, in a browser cookie without encryption.
Storing sensitive information in plain text within a cookie exposes it to immediate theft. Attackers can easily intercept or extract these cookies using common browser tools or network sniffers, gaining direct access to user credentials, session IDs, or other private data. Even if the data is encoded (e.g., using Base64), it does not provide security. Encoding is easily reversible, and attackers can quickly identify the encoding method and decode the information. To be secure, sensitive data in cookies must always be properly encrypted and integrity-protected.
Real-world impact

Real-world CVEs caused by CWE-315

  • CVE-2002-1800

    Admin password in cleartext in a cookie.

  • CVE-2001-1537

    Default configuration has cleartext usernames/passwords in cookie.

  • CVE-2001-1536

    Usernames/passwords in cleartext in cookies.

  • CVE-2005-2160

    Authentication information stored in cleartext in a cookie.

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

The following code excerpt stores a plaintext user account ID in a browser cookie.

Vulnerable Java 
response.addCookie( new Cookie("userAccountID", acctID) );
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-315

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Detection signals

How to detect CWE-315

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-315 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-315?

This vulnerability occurs when an application directly stores sensitive data, like session tokens or personal details, in a browser cookie without encryption.

How serious is CWE-315?

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-315?

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

How can I prevent CWE-315?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

How does Plexicus detect and fix CWE-315?

Plexicus's SAST engine matches the data-flow signature for CWE-315 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-315?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/315.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-315

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-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-526 Sibling

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…

Resources

Further reading

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