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CWE-335 Base Rascunho
Incorrect Usage of Seeds in Pseudo-Random Number Generator (PRNG)
This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) is used, but its initial seed value is not handled securely or predictably, compromising the randomness of its output.
Definição
What is CWE-335?
This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) is used, but its initial seed value is not handled securely or predictably, compromising the randomness of its output.
PRNGs are not truly random; they are deterministic algorithms that produce a sequence of numbers based on an initial seed. If an attacker can discover or guess this seed, they can predict the entire output stream, which is catastrophic for security functions like encryption keys, session tokens, or cryptographic nonces. Therefore, the seed must be treated with the same secrecy as a cryptographic key and should be generated from a robust, unpredictable source.
Secure seed management involves two critical practices. First, protect the seed itself as sensitive material—never hard-code it, log it, or transmit it insecurely. Second, source the seed from a cryptographically secure random number generator (CSPRNG) provided by the operating system or trusted library to ensure sufficient entropy. Avoid using predictable values like the current time, process IDs, or static strings, as these drastically reduce the number of possible seeds an attacker would need to guess.
Impacto no mundo real
Real-world CVEs caused by CWE-335
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Cloud application on Kubernetes generates passwords using a weak random number generator based on deployment time.
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server uses erlang:now() to seed the PRNG, which results in a small search space for potential random seeds
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Product's PRNG is not seeded for the generation of session IDs
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Router's PIN generation is based on rand(time(0)) seeding.
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 1
The following code uses a statistical PRNG to generate account IDs.
- 2
Because the program uses the same seed value for every invocation of the PRNG, its values are predictable, making the system vulnerable to attack.
- 3
Both of these examples use a statistical PRNG seeded with the current value of the system clock to generate a random number:
- 4
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).
- 5
This code grabs some random bytes and uses them for a seed in a PRNG, in order to generate a new cryptographic key.
Exemplo de código vulnerável
Vulnerable Java
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();
} Exemplo de código seguro
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Lista de verificação de prevenção
How to prevent CWE-335
- Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
- Implementation Validate input at trust boundaries; use allowlists, not denylists.
- Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
- Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
- Operation Monitor logs for the runtime signals listed in the next section.
Sinais de deteção
How to detect CWE-335
Executar testes dinâmicos de segurança de aplicações (DAST) contra o endpoint em execução.
Monitorizar os registos em tempo de execução para traços de exceção invulgares, input malformado ou tentativas de contornar a autorização.
Revisão de código: sinalizar qualquer novo código que trate input desta superfície sem usar os ajudantes validados do framework.
O Plexicus deteta automaticamente o CWE-335 e abre um PR de correção em menos de 60 segundos.
O Codex Remedium analisa cada commit, identifica esta fraqueza exata e entrega um pull request pronto para revisão com o patch. Sem tickets. Sem transferências.
Perguntas frequentes O que é o CWE-335?
Qual a gravidade do CWE-335?
Que linguagens ou plataformas são afetadas pelo CWE-335?
Como posso prevenir o CWE-335?
Como é que o Plexicus deteta e corrige o CWE-335?
Onde posso saber mais sobre o CWE-335?
Frequently asked questions
O que é o CWE-335?
This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) is used, but its initial seed value is not handled securely or predictably, compromising the randomness of its output.
Qual a gravidade do CWE-335?
A MITRE não publicou uma classificação de probabilidade de exploração para esta fraqueza. Trate-a como impacto médio até o seu modelo de ameaças provar o contrário.
Que linguagens ou plataformas são afetadas pelo CWE-335?
A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.
Como posso prevenir o CWE-335?
Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.
Como é que o Plexicus deteta e corrige o CWE-335?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-335 em cada commit. Quando é encontrada uma correspondência, o nosso agente Codex Remedium abre um PR de correção com o código corrigido, testes e um resumo de uma linha para o revisor.
Onde posso saber mais sobre o CWE-335?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/335.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
Weaknesses related to CWE-335
CWE-330 Pai
Use of Insufficiently Random Values
This vulnerability occurs when an application uses random values that are not sufficiently unpredictable in security-sensitive operations,…
CWE-1204 Irmão
Generation of Weak Initialization Vector (IV)
This vulnerability occurs when software uses a weak or predictable Initialization Vector (IV) for cryptographic operations. Many…
CWE-1241 Irmão
Use of Predictable Algorithm in Random Number Generator
This vulnerability occurs when a device or application relies on a predictable algorithm to generate pseudo-random numbers, making the…
CWE-331 Irmão
Insufficient Entropy
This vulnerability occurs when a system's random number generator or algorithm lacks sufficient unpredictability, creating patterns or…
CWE-334 Irmão
Small Space of Random Values
This vulnerability occurs when a system uses a random number generator that produces too few possible values. Attackers can easily predict…
CWE-338 Irmão
Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
This vulnerability occurs when software uses a pseudo-random number generator (PRNG) that is not cryptographically strong for…
CWE-340 Irmão
Generation of Predictable Numbers or Identifiers
This vulnerability occurs when a system creates numbers or identifiers that are too easy to guess, undermining security mechanisms that…
CWE-344 Irmão
Use of Invariant Value in Dynamically Changing Context
This vulnerability occurs when code uses a fixed, unchanging value (like a hardcoded string, number, or reference) in a situation where…
CWE-336 Filho
Same Seed in Pseudo-Random Number Generator (PRNG)
This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) is repeatedly initialized with the same starting seed value.
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