The product uses a Pseudo-Random Number Generator (PRNG) but does not correctly manage seeds.

PRNGs are deterministic and, while their output appears
random, they cannot actually create entropy. They rely on
cryptographically secure and unique seeds for entropy so
proper seeding is critical to the secure operation of the
PRNG.

Management of seeds could be broken down into two main areas:

(1) protecting seeds as cryptographic material (such as a cryptographic key);

(2) whenever possible, using a uniquely generated seed from
a cryptographically secure source

PRNGs require a seed as input to generate a stream of
numbers that are functionally indistinguishable from
random numbers. While the output is, in many cases,
sufficient for cryptographic uses, the output of any
PRNG is directly determined by the seed provided as
input. If the seed can be ascertained by a third party,
the entire output of the PRNG can be made known to
them. As such, the seed should be kept secret and
should ideally not be able to be guessed. For example,
the current time may be a poor seed. Knowing the
approximate time the PRNG was seeded greatly reduces
the possible key space.

Seeds do not necessarily need to be unique, but reusing seeds may open up attacks if the seed is discovered.

Primary

Resultant

Implementation
REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Access Control
Other
Bypass Protection Mechanism
Other
If a PRNG is used incorrectly, such as using the same seed for each initialization or using a predictable seed, then an attacker may be able to easily guess the seed and thus the random numbers. This could lead to unauthorized access to a system if the seed is used for authentication and authorization.

Automated Static Analysis
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.)

The following code uses a statistical PRNG to generate account IDs.

private static final long SEED = 1234567890;public int generateAccountID() {Random random = new Random(SEED);return random.nextInt();}

Because the program uses the same seed value for every invocation of the PRNG, its values are predictable, making the system vulnerable to attack.

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

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

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).

This code grabs some random bytes and uses them for a seed in a PRNG, in order to generate a new cryptographic key.

# getting 2 bytes of randomness for the seeding the PRNG
seed = os.urandom(2)
random.seed(a=seed)
key = random.getrandbits(128)

Since only 2 bytes are used as a seed, an attacker will only need to guess 2^16 (65,536) values before being able to replicate the state of the PRNG.

CVE-2020-7010
Cloud application on Kubernetes generates passwords using a weak random number generator based on deployment time.
https://www.cve.org/CVERecord?id=CVE-2020-7010

CVE-2019-11495
server uses erlang:now() to seed the PRNG, which
results in a small search space for potential random
seeds
https://www.cve.org/CVERecord?id=CVE-2019-11495

CVE-2018-12520
Product's PRNG is not seeded for the generation of session IDs
https://www.cve.org/CVERecord?id=CVE-2018-12520

CVE-2016-10180
Router's PIN generation is based on rand(time(0)) seeding.
https://www.cve.org/CVERecord?id=CVE-2016-10180

PRNG Seed Error

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

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.

PLOVER
2006-07-19
Draft 3
2006-07-19

Eric Dalci
Cigital
2008-07-01
updated Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated Common_Consequences, References, Relationships

CWE Content Team
MITRE
2017-11-08
updated Applicable_Platforms, Description, Modes_of_Introduction, Name, Relationships, Type

CWE Content Team
MITRE
2019-06-20
updated Relationships

CWE Content Team
MITRE
2020-02-24
updated Relationships

CWE Content Team
MITRE
2021-07-20
updated Description, Maintenance_Notes, Observed_Examples

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2022-10-13
updated Observed_Examples

CWE Content Team
MITRE
2023-01-31
updated Description

CWE Content Team
MITRE
2023-04-27
updated Relationships, Time_of_Introduction

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2023-10-26
updated Demonstrative_Examples

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Detection_Factors, Relationships, Weakness_Ordinalities

PRNG Seed Error