Executar análise estática (SAST) na base de código à procura do padrão inseguro no fluxo de dados.
CWE-1241 Base Rascunho
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 output sequence foreseeable.
Definição
What is CWE-1241?
This vulnerability occurs when a device or application relies on a predictable algorithm to generate pseudo-random numbers, making the output sequence foreseeable.
Pseudo-random number generators (PRNGs) create numbers using deterministic algorithms, meaning they have a finite internal state that will eventually repeat. This predictability makes them vulnerable to attacks where an adversary can analyze past outputs to deduce future values or uncover the generator's internal state, compromising the security of any system that depends on this randomness.
For robust security, especially in encryption, key generation, or session tokens, it's critical to use hardware-based True Random Number Generators (TRNGs). TRNGs derive randomness from unpredictable physical processes like electrical noise, producing outputs that are unbiased, independent, and fundamentally unpredictable, thereby providing a much stronger foundation for security-critical operations.
Impacto no mundo real
Real-world CVEs caused by CWE-1241
-
PHP framework uses mt_rand() function (Marsenne Twister) when generating tokens
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 1
Suppose a cryptographic function expects random value to be supplied for the crypto algorithm.
- 2
During the implementation phase, due to space constraint, a cryptographically secure random-number-generator could not be used, and instead of using a TRNG (True Random Number Generator), a LFSR (Linear Feedback Shift Register) is used to generate a random value. While an LFSR will provide a pseudo-random number, its entropy (measure of randomness) is insufficient for a cryptographic algorithm.
- 3
The example code is taken from the PRNG inside the buggy OpenPiton SoC of HACK@DAC'21 [REF-1370]. The SoC implements a pseudo-random number generator using a Linear Feedback Shift Register (LFSR).
- 4
An example of LFSR with the polynomial function P(x) = x 6+x 4+x 3+1 is shown in the figure.
- 5
A LFSR's input bit is determined by the output of a linear function of two or more of its previous states. Therefore, given a long cycle, a LFSR-based PRNG will enter a repeating cycle, which is predictable.
Exemplo de código vulnerável
Vulnerable Verilog
An example of LFSR with the polynomial function P(x) = x 6+x 4+x 3+1 is shown in the figure.
**reg in_sr, entropy16_valid;**
**reg [15:0] entropy16;**
**assign entropy16_o = entropy16;**
**assign entropy16_valid_o = entropy16_valid;**
**always @ (*)**
**begin**
```
```
in_sr = ^ (poly_i [15:0] & entropy16 [15:0]);**
**end** 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-1241
- Architecture and Design A true random number generator should be specified for cryptographic algorithms.
- Implementation A true random number generator should be implemented for cryptographic algorithms.
Sinais de deteção
How to detect CWE-1241
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-1241
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-1241?
Qual a gravidade do CWE-1241?
Que linguagens ou plataformas são afetadas pelo CWE-1241?
Como posso prevenir o CWE-1241?
Como é que o Plexicus deteta e corrige o CWE-1241?
Onde posso saber mais sobre o CWE-1241?
Frequently asked questions
O que é o CWE-1241?
This vulnerability occurs when a device or application relies on a predictable algorithm to generate pseudo-random numbers, making the output sequence foreseeable.
Qual a gravidade do CWE-1241?
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-1241?
MITRE lists the following affected platforms: System on Chip.
Como posso prevenir o CWE-1241?
A true random number generator should be specified for cryptographic algorithms. A true random number generator should be implemented for cryptographic algorithms.
Como é que o Plexicus deteta e corrige o CWE-1241?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-1241 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-1241?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/1241.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
Weaknesses related to CWE-1241
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-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-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…
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.