CWE - CWE-332: Insufficient Entropy in PRNG (4.18)

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CWE Glossary Definition

CWE-332: Insufficient Entropy in PRNG

Weakness ID: 332

Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
Abstraction: Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.

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Description

The lack of entropy available for, or used by, a Pseudo-Random Number Generator (PRNG) can be a stability and security threat.

Common Consequences

Section HelpThis table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

Impact	Details
DoS: Crash, Exit, or Restart	Scope: Availability If a pseudo-random number generator is using a limited entropy source which runs out (if the generator fails closed), the program may pause or crash.
Bypass Protection Mechanism; Other	Scope: Access Control, Other If a PRNG is using a limited entropy source which runs out, and the generator fails open, the generator could produce predictable random numbers. Potentially a weak source of random numbers could weaken the encryption method used for authentication of users.

Potential Mitigations

Phase(s)	Mitigation
Architecture and Design; Requirements	Strategy: Libraries or Frameworks 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.

Relationships

Section Help This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

Relevant to the view "Research Concepts" (View-1000)

Nature	Type	ID	Name
ChildOf	Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	331	Insufficient Entropy

Relevant to the view "Architectural Concepts" (View-1008)

Nature	Type	ID	Name
MemberOf	Category Category - a CWE entry that contains a set of other entries that share a common characteristic.	1013	Encrypt Data

Modes Of Introduction

Section HelpThe different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

Phase	Note
Architecture and Design
Implementation	REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Applicable Platforms

Section HelpThis listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Likelihood Of Exploit

Medium

Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Reference	Description
	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

Memberships

Section HelpThis MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.

Nature	Type	ID	Name
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	861	The CERT Oracle Secure Coding Standard for Java (2011) Chapter 18 - Miscellaneous (MSC)
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	905	SFP Primary Cluster: Predictability
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1152	SEI CERT Oracle Secure Coding Standard for Java - Guidelines 49. Miscellaneous (MSC)
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1414	Comprehensive Categorization: Randomness

Vulnerability Mapping Notes

Usage ALLOWED

(this CWE ID may be used to map to real-world vulnerabilities)

Reason Acceptable-Use

Rationale

This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments

Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Notes

Maintenance

As of CWE 4.5, terminology related to randomness, entropy, and predictability can vary widely. Within the developer and other communities, "randomness" is used heavily. However, within cryptography, "entropy" is distinct, typically implied as a measurement. There are no commonly-used definitions, even within standards documents and cryptography papers. Future versions of CWE will attempt to define these terms and, if necessary, distinguish between them in ways that are appropriate for different communities but do not reduce the usability of CWE for mapping, understanding, or other scenarios.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CLASP	Insufficient entropy in PRNG
The CERT Oracle Secure Coding Standard for Java (2011)	MSC02-J	Generate strong random numbers

References

[REF-267] Information Technology Laboratory, National Institute of Standards and Technology. "FIPS PUB 140-2: SECURITY REQUIREMENTS FOR CRYPTOGRAPHIC MODULES". 2001年05月25日.
<https://csrc.nist.gov/files/pubs/fips/140-2/upd2/final/docs/fips1402.pdf>. (URL validated: 2025年05月21日)

[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005.
<https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>. (URL validated: 2024年11月17日)

[REF-1374] Unciphered. "Randstorm: You Can't Patch a House of Cards". 2023年11月14日.
<https://www.unciphered.com/disclosure-of-vulnerable-bitcoin-wallet-library-2/>. (URL validated: 2025年07月29日)

Content History

Submissions
Submission Date	Submitter	Organization
2006年07月19日 (CWE Draft 3, 2006年07月19日)	CLASP
2006年07月19日 (CWE Draft 3, 2006年07月19日)
Modifications
Modification Date	Modifier	Organization
2025年09月09日 (CWE 4.18, 2025年09月09日)	CWE Content Team	MITRE
2025年09月09日 (CWE 4.18, 2025年09月09日)	updated References
2024年02月29日 (CWE 4.14, 2024年02月29日)	CWE Content Team	MITRE
2024年02月29日 (CWE 4.14, 2024年02月29日)	updated Observed_Examples, References
2023年06月29日	CWE Content Team	MITRE
2023年06月29日	updated Mapping_Notes
2023年04月27日	CWE Content Team	MITRE
2023年04月27日	updated References, Relationships
2021年10月28日	CWE Content Team	MITRE
2021年10月28日	updated Observed_Examples
2021年07月20日	CWE Content Team	MITRE
2021年07月20日	updated Maintenance_Notes
2021年03月15日	CWE Content Team	MITRE
2021年03月15日	updated References
2020年02月24日	CWE Content Team	MITRE
2020年02月24日	updated Relationships
2019年06月20日	CWE Content Team	MITRE
2019年06月20日	updated Relationships
2019年01月03日	CWE Content Team	MITRE
2019年01月03日	updated Relationships, Taxonomy_Mappings
2017年11月08日	CWE Content Team	MITRE
2017年11月08日	updated Applicable_Platforms, Modes_of_Introduction, References, Relationships
2015年12月07日	CWE Content Team	MITRE
2015年12月07日	updated Relationships
2012年05月11日	CWE Content Team	MITRE
2012年05月11日	updated Common_Consequences, Demonstrative_Examples, Relationships
2011年09月13日	CWE Content Team	MITRE
2011年09月13日	updated Potential_Mitigations, References
2011年06月01日	CWE Content Team	MITRE
2011年06月01日	updated Common_Consequences, Demonstrative_Examples, Relationships, Taxonomy_Mappings
2010年06月21日	CWE Content Team	MITRE
2010年06月21日	updated Potential_Mitigations
2009年12月28日	CWE Content Team	MITRE
2009年12月28日	updated Potential_Mitigations
2009年03月10日	CWE Content Team	MITRE
2009年03月10日	updated Potential_Mitigations
2008年09月08日	CWE Content Team	MITRE
2008年09月08日	updated Common_Consequences, Relationships, Taxonomy_Mappings
2008年07月01日	Eric Dalci	Cigital
2008年07月01日	updated Time_of_Introduction

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Page Last Updated: September 09, 2025

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