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

Description

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

Submission Date :

July 19, 2006, midnight

Modification Date :

2023-06-29 00:00:00+00:00

Organization :

MITRE

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.

Example Vulnerable Codes

Example - 1

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).

Related Weaknesses

This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined to give an overview of the different insight to similar items that may exist at higher and lower levels of abstraction.

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

Go to

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