Executar análise estática (SAST) na base de código à procura do padrão inseguro no fluxo de dados.
CWE-331 Base Rascunho
Insufficient Entropy
This vulnerability occurs when a system's random number generator or algorithm lacks sufficient unpredictability, creating patterns or predictable outputs that are easier for attackers to guess.
Definição
What is CWE-331?
This vulnerability occurs when a system's random number generator or algorithm lacks sufficient unpredictability, creating patterns or predictable outputs that are easier for attackers to guess.
Insufficient entropy means your random values aren't random enough. This often stems from using weak algorithms (like `rand()`), seeding generators with predictable values (like the current time), or drawing from a source with limited possible outcomes. Attackers can exploit these patterns to predict security-critical values like session tokens, cryptographic keys, or password reset codes, effectively bypassing protections that rely on randomness.
To prevent this, developers should use cryptographically secure pseudorandom number generators (CSPRNGs) provided by the operating system or language's security libraries. Always ensure your entropy source is robust and unpredictable, especially for initialization vectors, nonces, and key generation. For high-stakes systems, consider using hardware random number generators or dedicated security services to guarantee the quality of your randomness.
Impacto no mundo real
Real-world CVEs caused by CWE-331
-
Insufficiently random data used to generate session tokens using C rand(). Also, for certificate/key generation, uses a source that does not block when entropy is low.
-
Chain: insufficient precision (CWE-1339) in random-number generator causes some zero bits to be reliably generated, reducing the amount of entropy (CWE-331)
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 1
This code generates a unique random identifier for a user's session.
- 2
Because the seed for the PRNG is always the user's ID, the session ID will always be the same. An attacker could thus predict any user's session ID and potentially hijack the session.
- 3
This example also exhibits a Small Seed Space (CWE-339).
- 4
The following code uses a statistical PRNG to create a URL for a receipt that remains active for some period of time after a purchase.
- 5
This code uses the Random.nextInt() function to generate "unique" identifiers for the receipt pages it generates. Because Random.nextInt() is a statistical PRNG, it is easy for an attacker to guess the strings it generates. Although the underlying design of the receipt system is also faulty, it would be more secure if it used a random number generator that did not produce predictable receipt identifiers, such as a cryptographic PRNG.
Exemplo de código vulnerável
Vulnerable PHP
This code generates a unique random identifier for a user's session.
function generateSessionID($userID){
srand($userID);
return rand();
} 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-331
- Implementation Determine the necessary entropy to adequately provide for randomness and predictability. This can be achieved by increasing the number of bits of objects such as keys and seeds.
Sinais de deteção
How to detect CWE-331
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.
CWE-331
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Perguntas frequentes O que é o CWE-331?
Qual a gravidade do CWE-331?
Que linguagens ou plataformas são afetadas pelo CWE-331?
Como posso prevenir o CWE-331?
Como é que o Plexicus deteta e corrige o CWE-331?
Onde posso saber mais sobre o CWE-331?
Frequently asked questions
O que é o CWE-331?
This vulnerability occurs when a system's random number generator or algorithm lacks sufficient unpredictability, creating patterns or predictable outputs that are easier for attackers to guess.
Qual a gravidade do CWE-331?
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-331?
A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.
Como posso prevenir o CWE-331?
Determine the necessary entropy to adequately provide for randomness and predictability. This can be achieved by increasing the number of bits of objects such as keys and seeds.
Como é que o Plexicus deteta e corrige o CWE-331?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-331 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-331?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/331.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
Weaknesses related to CWE-331
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-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-335 Irmão
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…
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-332 Filho
Insufficient Entropy in PRNG
This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) doesn't have enough randomness (entropy) to start with, or isn't…
Pronto para validar o que importa?
Pronto para validar o que importa.
O Plexicus é Proof-Driven AppSec: achados validados, compreensão contextual e remediação revisada — ancorada em evidência, escopada com você.