CWE-333: Improper Handling of Insufficient Entropy in TRNG

Code Examples & CVEs

Demonstrative Examples

This code uses a TRNG to generate a unique session id for new connections to a server:

This code does not attempt to limit the number of new connections or make sure the TRNG can successfully generate a new random number. An attacker may be able to create many new connections and exhaust the entropy of the TRNG. The TRNG may then block and cause the program to crash or hang.

BadC

while (1){                         if (haveNewConnection()){if (hwRandom()){int sessionID = hwRandom();createNewConnection(sessionID);} } }

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-333 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-333, Improper Handling of Insufficient Entropy in TRNG, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Improper Handling of Insufficient Entropy in TRNG during Implementation

MITRE associates mitigation with Implementation; recorded impacts include DoS: Crash, Exit, or Restart; related weaknesses include CWE-331, and CWE-755. Use these source-defined anchors to turn CWE-333 into implementation, review, and verification checks for the affected component.

CWE-333: Improper Handling of Insufficient Entropy in TRNG — MITRE CWE

Triage CWE-333 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-333, Improper Handling of Insufficient Entropy in TRNG, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-333

Apply MITRE's full root-cause mapping guidance when using CWE-333, Improper Handling of Insufficient Entropy in TRNG. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-333 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-333, Improper Handling of Insufficient Entropy in TRNG. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-333: Improper Handling of Insufficient Entropy in TRNG?+

CWE-333: Improper Handling of Insufficient Entropy in TRNG is a Common Weakness Enumeration (CWE) entry maintained by MITRE. True random number generators (TRNG) generally have a limited source of entropy and therefore can fail or block. The rate at which true random numbers can be generated is limited. It is important that one uses them only when they are needed for security.

What are the security consequences of Improper Handling of Insufficient Entropy in TRNG?+

If exploited, CWE-333 (Improper Handling of Insufficient Entropy in TRNG) it can compromise Availability, leading to outcomes such as DoS: Crash, Exit, or Restart.

How do you prevent or mitigate Improper Handling of Insufficient Entropy in TRNG?+

Recommended mitigations for CWE-333 include: Rather than failing on a lack of random numbers, it is often preferable to wait for more numbers to be created.

Which programming languages are affected by Improper Handling of Insufficient Entropy in TRNG?+

CWE-333 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-333 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-333: Improper Handling of Insufficient Entropy in TRNG

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