CWE-1204 Base Incompleto

Generation of Weak Initialization Vector (IV)

This vulnerability occurs when software uses a weak or predictable Initialization Vector (IV) for cryptographic operations. Many encryption algorithms require IVs to be both unique and unpredictable…

Definição

What is CWE-1204?

This vulnerability occurs when software uses a weak or predictable Initialization Vector (IV) for cryptographic operations. Many encryption algorithms require IVs to be both unique and unpredictable to ensure security, and failing to meet these requirements can compromise the entire encryption process.
Certain encryption methods, like block ciphers in specific modes, rely heavily on strong Initialization Vectors. The IV must be both unique (never reused with the same key) and unpredictable (random) to prevent attackers from deducing patterns or recovering plaintext. If the IV generation is flawed—due to a bug, a poor random source, or a reused value—the cryptographic protection can be significantly weakened. In practice, attacking a weak IV is often easier than breaking the core cipher. Attackers can exploit predictable or repeated IVs to perform decryption, reveal data patterns, or bypass security entirely. Therefore, developers must ensure their IV generation adheres strictly to the requirements of the specific cryptographic primitive being used.
Impacto no mundo real

Real-world CVEs caused by CWE-1204

  • CVE-2020-1472

    ZeroLogon vulnerability - use of a static IV of all zeroes in AES-CFB8 mode

  • CVE-2011-3389

    BEAST attack in SSL 3.0 / TLS 1.0. In CBC mode, chained initialization vectors are non-random, allowing decryption of HTTPS traffic using a chosen plaintext attack.

  • CVE-2001-0161

    wireless router does not use 6 of the 24 bits for WEP encryption, making it easier for attackers to decrypt traffic

  • CVE-2001-0160

    WEP card generates predictable IV values, making it easier for attackers to decrypt traffic

  • CVE-2017-3225

    device bootloader uses a zero initialization vector during AES-CBC

  • CVE-2016-6485

    crypto framework uses PHP rand function - which is not cryptographically secure - for an initialization vector

  • CVE-2014-5386

    encryption routine does not seed the random number generator, causing the same initialization vector to be generated repeatedly

  • CVE-2020-5408

    encryption functionality in an authentication framework uses a fixed null IV with CBC mode, allowing attackers to decrypt traffic in applications that use this functionality

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    In the following examples, CBC mode is used when encrypting data:

  2. 2

    In both of these examples, the initialization vector (IV) is always a block of zeros. This makes the resulting cipher text much more predictable and susceptible to a dictionary attack.

  3. 3

    The Wired Equivalent Privacy (WEP) protocol used in the 802.11 wireless standard only supported 40-bit keys, and the IVs were only 24 bits, increasing the chances that the same IV would be reused for multiple messages. The IV was included in plaintext as part of the packet, making it directly observable to attackers. Only 5000 messages are needed before a collision occurs due to the "birthday paradox" [REF-1176]. Some implementations would reuse the same IV for each packet. This IV reuse made it much easier for attackers to recover plaintext from two packets with the same IV, using well-understood attacks, especially if the plaintext was known for one of the packets [REF-1175].

Exemplo de código vulnerável

Vulnerable C

In the following examples, CBC mode is used when encrypting data:

Vulnerável C 
EVP_CIPHER_CTX ctx;
  char key[EVP_MAX_KEY_LENGTH];
  char iv[EVP_MAX_IV_LENGTH];
  RAND_bytes(key, b);
  memset(iv,0,EVP_MAX_IV_LENGTH);
  EVP_EncryptInit(&ctx,EVP_bf_cbc(), key,iv);
Exemplo de código seguro

Secure pseudo

Seguro 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-1204

  • Implementation Different cipher modes have different requirements for their IVs. When choosing and implementing a mode, it is important to understand those requirements in order to keep security guarantees intact. Generally, it is safest to generate a random IV, since it will be both unpredictable and have a very low chance of being non-unique. IVs do not have to be kept secret, so if generating duplicate IVs is a concern, a list of already-used IVs can be kept and checked against. NIST offers recommendations on generation of IVs for modes of which they have approved. These include options for when random IVs are not practical. For CBC, CFB, and OFB, see [REF-1175]; for GCM, see [REF-1178].
Sinais de deteção

How to detect CWE-1204

SAST High

Executar análise estática (SAST) na base de código à procura do padrão inseguro no fluxo de dados.

DAST Moderate

Executar testes dinâmicos de segurança de aplicações (DAST) contra o endpoint em execução.

Runtime Moderate

Monitorizar os registos em tempo de execução para traços de exceção invulgares, input malformado ou tentativas de contornar a autorização.

Code review Moderate

Revisão de código: sinalizar qualquer novo código que trate input desta superfície sem usar os ajudantes validados do framework.

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-1204 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.

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Perguntas frequentes

Frequently asked questions

O que é o CWE-1204?

This vulnerability occurs when software uses a weak or predictable Initialization Vector (IV) for cryptographic operations. Many encryption algorithms require IVs to be both unique and unpredictable to ensure security, and failing to meet these requirements can compromise the entire encryption process.

Qual a gravidade do CWE-1204?

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-1204?

A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.

Como posso prevenir o CWE-1204?

Different cipher modes have different requirements for their IVs. When choosing and implementing a mode, it is important to understand those requirements in order to keep security guarantees intact. Generally, it is safest to generate a random IV, since it will be both unpredictable and have a very low chance of being non-unique. IVs do not have to be kept secret, so if generating duplicate IVs is a concern, a list of already-used IVs can be kept and checked against. NIST offers…

Como é que o Plexicus deteta e corrige o CWE-1204?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-1204 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-1204?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/1204.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

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CWE-329 Filho

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Recursos

Further reading

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