CWE-257 Base Incomplete High likelihood

Storing Passwords in a Recoverable Format

This vulnerability occurs when an application stores user passwords in a format that can be easily reversed or decrypted back to their original plaintext form. This practice, often called storing…

Definition

What is CWE-257?

This vulnerability occurs when an application stores user passwords in a format that can be easily reversed or decrypted back to their original plaintext form. This practice, often called storing 'recoverable' passwords, defeats the core purpose of password protection. It allows anyone with access to the stored data—including attackers who breach the system or even malicious insiders—to obtain and reuse the actual passwords on other accounts, offering no real security advantage over storing them in plain text.
When passwords are stored in a recoverable format, such as using weak or reversible encryption instead of a proper one-way hash, the system inherently retains the ability to convert them back. This creates a single point of failure: if the storage is compromised or accessed by an unauthorized party, every password becomes immediately usable for account takeover and credential stuffing attacks across other services. The risk is identical to storing plaintext passwords, as the decryption key or method is typically accessible within the application's environment. From a security perspective, there is no legitimate operational need for developers or system administrators to retrieve a user's original password. Standard authentication should compare a one-way hash of the entered password against a stored hash. Any design that requires password recovery is flawed; a secure system should only offer a password reset function. Relying on reversible storage undermines user trust and system integrity, as it enables abuse by both external attackers and privileged insiders who can decrypt credentials at will.
Real-world impact

Real-world CVEs caused by CWE-257

  • A messaging platform serializes all elements of User/Group objects, making private information available to adversaries

How attackers exploit it

Step-by-step attacker path

  1. 1

    Both of these examples verify a password by comparing it to a stored compressed version.

  2. 2

    Because a compression algorithm is used instead of a one way hashing algorithm, an attacker can recover compressed passwords stored in the database.

  3. 3

    The following examples show a portion of properties and configuration files for Java and ASP.NET applications. The files include username and password information but they are stored in cleartext.

  4. 4

    This Java example shows a properties file with a cleartext username / password pair.

  5. 5

    The following example shows a portion of a configuration file for an ASP.Net application. This configuration file includes username and password information for a connection to a database but the pair is stored in cleartext.

Vulnerable code example

Vulnerable C

Both of these examples verify a password by comparing it to a stored compressed version.

Vulnerable C
int VerifyAdmin(char *password) {
  	if (strcmp(compress(password), compressed_password)) {
  		printf("Incorrect Password!\n");
  		return(0);
  	}
  	printf("Entering Diagnostic Mode...\n");
  	return(1);
  }
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-257

  • Architecture and Design Use strong, non-reversible encryption to protect stored passwords.
Detection signals

How to detect CWE-257

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-257 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.

Frequently asked questions

Frequently asked questions

What is CWE-257?

This vulnerability occurs when an application stores user passwords in a format that can be easily reversed or decrypted back to their original plaintext form. This practice, often called storing 'recoverable' passwords, defeats the core purpose of password protection.

How serious is CWE-257?

MITRE rates the likelihood of exploit as High — this weakness is actively exploited in the wild and should be prioritized for remediation.

What languages or platforms are affected by CWE-257?

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

How can I prevent CWE-257?

Use strong, non-reversible encryption to protect stored passwords.

How does Plexicus detect and fix CWE-257?

Plexicus's SAST engine matches the data-flow signature for CWE-257 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-257?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/257.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Ready when you are

Don't Let Security
Weigh You Down.

Stop choosing between AI velocity and security debt. Plexicus is the only platform that runs Vibe Coding Security and ASPM in parallel — one workflow, every codebase.