CWE-339
Weakness AllowedSmall Seed Space in PRNG
Abstraction: Variant · Status: Draft
A Pseudo-Random Number Generator (PRNG) uses a relatively small seed space, which makes it more susceptible to brute force attacks.
PRNGs are entirely deterministic once seeded, so it should be extremely difficult to guess the seed. If an attacker can collect the outputs of a PRNG and then brute force the seed by trying every possibility to see which seed matches the observed output, then the attacker will know the output of any subsequent calls to the PRNG. A small seed space implies that the attacker will have far fewer possible values to try to exhaust all possibilities.
Mapping guidance
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.
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.
Relationships and members
Modes of introduction
REALIZATION: This weakness is caused during implementation of an architectural security tactic.
Notes
Maintenance
This entry may have a chaining relationship with predictable from observable state (CWE-341).
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.
Content history
updated Time_of_Introduction
updated Maintenance_Notes, Relationships, Taxonomy_Mappings
updated Potential_Mitigations
updated Potential_Mitigations
updated Observed_Examples, Potential_Mitigations
updated Common_Consequences
updated Common_Consequences
updated Potential_Mitigations, References
updated Relationships
updated Potential_Mitigations
updated Applicable_Platforms, Modes_of_Introduction, References, Relationships
updated Type
updated Relationships
updated Maintenance_Notes
updated Demonstrative_Examples, Description, Maintenance_Notes, Observed_Examples, Potential_Mitigations, References
updated References, Relationships, Time_of_Introduction
updated Mapping_Notes
updated Demonstrative_Examples
updated References
updated Weakness_Ordinalities
3 vulnerabilities reference this CWE, most recent first.
CVE-2026-2815 (GCVE-0-2026-2815)
Vulnerability from cvelistv5 – Published: 2026-06-25 13:27 – Updated: 2026-06-25 14:03- CWE-339 - Small seed space in PRNG
| URL | Tags |
|---|---|
| https://siliconlabs.lightning.force.com/sfc/servl… | vendor-advisorypermissions-required |
| https://github.com/SiliconLabsSoftware/sisdk-release | patch |
| Vendor | Product | Version | |
|---|---|---|---|
| Silicon Labs | SiSDK |
Affected:
0 , ≤ 2025.12.1
(semver)
|
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CVE-2024-10026 (GCVE-0-2024-10026)
Vulnerability from cvelistv5 – Published: 2025-01-30 19:12 – Updated: 2025-02-24 11:50{
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GHSA-F2CJ-J66G-55WJ
Vulnerability from github – Published: 2026-06-25 15:32 – Updated: 2026-06-25 15:32Incorrect use of the PUF key for user key generation in EFR32xG27 results in predictable keys
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Mitigation
Use well vetted pseudo-random number generating algorithms with adequate length seeds. Pseudo-random number generators can produce predictable numbers if the generator is known and the seed can be guessed. A 256-bit seed is a good starting point for producing a "random enough" number.
Mitigation MIT-2
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.
No CAPEC attack patterns related to this CWE.