CWE-336: Same Seed in Pseudo-Random Number Generator (PRNG)
A Pseudo-Random Number Generator (PRNG) uses the same seed each time the product is initialized.
How it's found
Same Seed in Pseudo-Random Number Generator (PRNG) is a specific, narrowly defined instance of a broader pattern. Testers confirm it with targeted code review and a proof-of-concept input that exercises the exact code path this weakness describes.
Given the deterministic nature of PRNGs, using the same seed for each initialization will lead to the same output in the same order. If an attacker can guess (or knows) the seed, then the attacker may be able to determine the random numbers that will be produced from the PRNG.
Consequences
- Other, Bypass Protection Mechanism
Mitigations
- Architecture and Design: Do not reuse PRNG seeds. Consider a PRNG that periodically re-seeds itself as needed from a high quality pseudo-random output, such as hardware devices.
- Architecture and Design/Requirements: 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.
Where this fits in a TurboPentest engagement
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Frequently asked questions
What is CWE-336?
A Pseudo-Random Number Generator (PRNG) uses the same seed each time the product is initialized.
How do you find Same Seed in Pseudo-Random Number Generator (PRNG)?
Same Seed in Pseudo-Random Number Generator (PRNG) is a specific, narrowly defined instance of a broader pattern. Testers confirm it with targeted code review and a proof-of-concept input that exercises the exact code path this weakness describes.
What is the impact of CWE-336?
Other, Bypass Protection Mechanism
Does TurboPentest test for Same Seed in Pseudo-Random Number Generator (PRNG)?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Related CWEs
Written and reviewed by
Michel Chamberland - Founder & CEO, IntegSec
CISSP, OSCP, OSCE, CEH, GIAC, CCSK · 20+ years in offensive security
Michel has spent 20+ years on offensive security teams including IBM X-Force Red and Trustwave SpiderLabs, leading penetration tests, red team engagements, and breach response for Fortune 500 customers. He is the founder of IntegSec and the architect of TurboPentest.
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