CWE - CWE-337: Predictable Seed in Pseudo-Random Number Generator (PRNG) (4.18)

Home > CWE List > CWE-337: Predictable Seed in Pseudo-Random Number Generator (PRNG) (4.18)

CWE Glossary Definition

CWE-337: Predictable Seed in Pseudo-Random Number Generator (PRNG)

Weakness ID: 337

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.

View customized information:

For users who are interested in more notional aspects of a weakness. Example: educators, technical writers, and project/program managers. For users who are concerned with the practical application and details about the nature of a weakness and how to prevent it from happening. Example: tool developers, security researchers, pen-testers, incident response analysts. For users who are mapping an issue to CWE/CAPEC IDs, i.e., finding the most appropriate CWE for a specific issue (e.g., a CVE record). Example: tool developers, security researchers. For users who wish to see all available information for the CWE/CAPEC entry. For users who want to customize what details are displayed.

Edit Custom Filter

Description

A Pseudo-Random Number Generator (PRNG) is initialized from a predictable seed, such as the process ID or system time.

Extended Description

The use of predictable seeds significantly reduces the number of possible seeds that an attacker would need to test in order to predict which random numbers will be generated by the PRNG.

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
Varies by Context	Scope: Other

Potential Mitigations

Phase(s)	Mitigation
Use non-predictable inputs for seed generation.
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, or use the more recent FIPS 140-3 [REF-1192] if possible.
Implementation	Use a PRNG that periodically re-seeds itself using input from high-quality sources, such as hardware devices with high entropy. However, do not re-seed too frequently, or else the entropy source might block.

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.	335	Incorrect Usage of Seeds in Pseudo-Random Number Generator (PRNG)

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
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)

Demonstrative Examples

Example 1

Both of these examples use a statistical PRNG seeded with the current value of the system clock to generate a random number:

(bad code)

Example Language: Java

Random random = new Random(System.currentTimeMillis());
int accountID = random.nextInt();

(bad code)

Example Language: C

srand(time());
int randNum = rand();

An attacker can easily predict the seed used by these PRNGs, and so also predict the stream of random numbers generated. Note these examples also exhibit CWE-338 (Use of Cryptographically Weak PRNG).

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
CVE-2020-7010	Cloud application on Kubernetes generates passwords using a weak random number generator based on deployment time.
CVE-2019-11495	server uses erlang:now() to seed the PRNG, which results in a small search space for potential random seeds
CVE-2008-0166	The removal of a couple lines of code caused Debian's OpenSSL Package to only use the current process ID for seeding a PRNG
CVE-2016-10180	Router's PIN generation is based on rand(time(0)) seeding.
CVE-2018-9057	cloud provider product uses a non-cryptographically secure PRNG and seeds it with the current time

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.	1346	OWASP Top Ten 2021 Category A02:2021 - Cryptographic Failures
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1366	ICS Communications: Frail Security in Protocols
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
PLOVER	Predictable Seed 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". Annex C, Approved Random Number Generators. 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-1192] Information Technology Laboratory, National Institute of Standards and Technology. "FIPS PUB 140-3: SECURITY REQUIREMENTS FOR CRYPTOGRAPHIC MODULES". 2019年03月22日.
<https://csrc.nist.gov/publications/detail/fips/140/3/final>.

[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 20: Weak Random Numbers." Page 299. McGraw-Hill. 2010.

Content History

Submissions
Submission Date	Submitter	Organization
2006年07月19日 (CWE Draft 3, 2006年07月19日)	PLOVER
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
2023年06月29日	CWE Content Team	MITRE
2023年06月29日	updated Mapping_Notes, Relationships
2023年04月27日	CWE Content Team	MITRE
2023年04月27日	updated References, Relationships, Time_of_Introduction
2022年10月13日	CWE Content Team	MITRE
2022年10月13日	updated Observed_Examples
2021年10月28日	CWE Content Team	MITRE
2021年10月28日	updated Relationships
2021年07月20日	CWE Content Team	MITRE
2021年07月20日	updated Maintenance_Notes, Observed_Examples, Potential_Mitigations, References
2020年02月24日	CWE Content Team	MITRE
2020年02月24日	updated Description, Relationships
2019年06月20日	CWE Content Team	MITRE
2019年06月20日	updated Type
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, Demonstrative_Examples, Description, Modes_of_Introduction, Name, References, Relationships
2012年10月30日	CWE Content Team	MITRE
2012年10月30日	updated Demonstrative_Examples, Potential_Mitigations
2012年05月11日	CWE Content Team	MITRE
2012年05月11日	updated References, 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27日	CWE Content Team	MITRE
2011年06月27日	updated Common_Consequences
2011年06月01日	CWE Content Team	MITRE
2011年06月01日	updated Common_Consequences, 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 Relationships, Taxonomy_Mappings
2008年07月01日	Eric Dalci	Cigital
2008年07月01日	updated Time_of_Introduction
2008年07月01日	Sean Eidemiller	Cigital
2008年07月01日	added/updated demonstrative examples
Previous Entry Names
Change Date	Previous Entry Name
2017年11月08日	Predictable Seed in PRNG

More information is available — Please edit the custom filter or select a different filter.

Page Last Updated: September 09, 2025

MITRE

Use of the Common Weakness Enumeration (CWE™) and the associated references from this website are subject to the Terms of Use. CWE is sponsored by the U.S. Department of Homeland Security (DHS) Cybersecurity and Infrastructure Security Agency (CISA) and managed by the Homeland Security Systems Engineering and Development Institute (HSSEDI) which is operated by The MITRE Corporation (MITRE). Copyright © 2006–2025, The MITRE Corporation. CWE, CWSS, CWRAF, and the CWE logo are trademarks of The MITRE Corporation.

HSSEDI