CWE-549 Base Draft

Missing Password Field Masking

This vulnerability occurs when an application fails to hide password characters as they are typed, making them visible to anyone who can see the screen. This exposes user credentials to onlookers or…

Definition

What is CWE-549?

This vulnerability occurs when an application fails to hide password characters as they are typed, making them visible to anyone who can see the screen. This exposes user credentials to onlookers or screen-capturing malware.
Password masking is a fundamental security feature that protects credentials from 'shoulder surfing'—where someone physically observes the screen—and from software that may capture screen content. When this visual protection is missing, even a brief exposure can lead to a compromised account, as passwords are entered in plain sight. For developers, the fix is straightforward: always use an input field with its type attribute set to 'password' in HTML, or the equivalent secure text entry component in your chosen UI framework. This ensures the field automatically obscures each character, typically with dots or asterisks, providing a critical layer of privacy during authentication without affecting functionality.
Real-world impact

Real-world CVEs caused by CWE-549

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-549

  • Implementation / Requirements Recommendations include requiring all password fields in your web application be masked to prevent other users from seeing this information.
Detection signals

How to detect CWE-549

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-549 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-549?

This vulnerability occurs when an application fails to hide password characters as they are typed, making them visible to anyone who can see the screen. This exposes user credentials to onlookers or screen-capturing malware.

How serious is CWE-549?

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-549?

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

How can I prevent CWE-549?

Recommendations include requiring all password fields in your web application be masked to prevent other users from seeing this information.

How does Plexicus detect and fix CWE-549?

Plexicus's SAST engine matches the data-flow signature for CWE-549 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-549?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/549.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-549

CWE-522 Parent

Insufficiently Protected Credentials

This vulnerability occurs when an application handles sensitive credentials like passwords or API keys in an insecure way, making them…

CWE-256 Sibling

Plaintext Storage of a Password

This vulnerability occurs when an application stores user passwords as readable text instead of using secure, one-way hashing. This…

CWE-257 Sibling

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…

CWE-260 Sibling

Password in Configuration File

This vulnerability occurs when an application stores sensitive passwords directly within a configuration file, making them easily readable…

CWE-261 Sibling

Weak Encoding for Password

Using simple encoding like Base64 to hide a password provides no real security, as it can be easily reversed.

CWE-523 Sibling

Unprotected Transport of Credentials

This vulnerability occurs when a login page or authentication system transmits user credentials (like usernames and passwords) over a…

Resources

Further reading

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