CWE-332 Variant Draft Medium likelihood

Insufficient Entropy in PRNG

This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) doesn't have enough randomness (entropy) to start with, or isn't using enough during operation. This makes its outputs…

Definition

What is CWE-332?

This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) doesn't have enough randomness (entropy) to start with, or isn't using enough during operation. This makes its outputs predictable, undermining both system stability and security.

Insufficient entropy means the PRNG's starting state or its ongoing process lacks true randomness. Instead of producing unpredictable sequences, it may generate numbers that are weak, repeatable, or follow detectable patterns. Attackers can exploit this predictability to guess security tokens, cryptographic keys, or session identifiers, leading directly to breaches like session hijacking or data decryption. For developers, the core issue often lies in using default or poorly seeded PRNGs, especially in virtualized or embedded environments where entropy sources (like user input or hardware events) are limited. To prevent this, always use cryptographically secure PRNGs (CSPRNGs) provided by your platform's security libraries, ensure they are properly seeded with high-quality entropy from reliable system sources, and avoid creating your own random number generation algorithms.

Real-world impact

Real-world CVEs caused by CWE-332

[REF-1374]

Chain: JavaScript-based cryptocurrency library can fall back to the insecure Math.random() function instead of reporting a failure (CWE-392), thus reducing the entropy (CWE-332) and leading to generation of non-unique cryptographic keys for Bitcoin wallets (CWE-1391)
CVE-2019-1715

security product has insufficient entropy in the DRBG, allowing collisions and private key discovery

How attackers exploit it

Step-by-step attacker path

1
Identify a code path that handles untrusted input without validation.
2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
3
Deliver the payload through a normal request and observe the application's reaction.
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

// 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-332

Architecture and Design / Requirements Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems. Consult FIPS 140-2 Annex C ("Approved Random Number Generators").
Implementation Consider a PRNG that re-seeds itself as needed from high-quality pseudo-random output, such as hardware devices.
Architecture and Design When deciding which PRNG to use, look at its sources of entropy. Depending on what your security needs are, you may need to use a random number generator that always uses strong random data -- i.e., a random number generator that attempts to be strong but will fail in a weak way or will always provide some middle ground of protection through techniques like re-seeding. Generally, something that always provides a predictable amount of strength is preferable.

Detection signals

How to detect CWE-332

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

Plexicus auto-fix

Plexicus auto-detects CWE-332 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

What is CWE-332?

How serious is CWE-332?

MITRE rates the likelihood of exploit as Medium — exploitation is realistic but typically requires specific conditions.

What languages or platforms are affected by CWE-332?

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

How can I prevent CWE-332?

Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems. Consult FIPS 140-2 Annex C ("Approved Random Number Generators"). Consider a PRNG that re-seeds itself as needed from high-quality pseudo-random output, such as hardware devices.

How does Plexicus detect and fix CWE-332?

Plexicus's SAST engine matches the data-flow signature for CWE-332 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-332?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/332.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-332

CWE-331 Parent