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…

Definición

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 en el 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

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  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].

Ejemplo de código vulnerable

Vulnerable C

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

Vulnerable 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);
Ejemplo 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 prevención

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].
Señales de detección

How to detect CWE-1204

SAST High

Ejecuta análisis estático (SAST) sobre el código buscando el patrón inseguro en el flujo de datos.

DAST Moderate

Ejecuta pruebas dinámicas de seguridad de aplicaciones (DAST) contra el endpoint en vivo.

Runtime Moderate

Vigila los logs en tiempo de ejecución para detectar trazas de excepción inusuales, entradas malformadas o intentos de bypass de autorización.

Code review Moderate

Revisión de código: marca cualquier código nuevo que maneje entrada desde esta superficie sin usar los helpers validados del framework.

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-1204 y abre un PR de corrección en menos de 60 segundos.

Codex Remedium escanea cada commit, identifica esta debilidad concreta y entrega un pull request listo para revisión con el parche. Sin tickets. Sin traspasos.

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Preguntas frecuentes

Frequently asked questions

¿Qué es 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.

¿Qué gravedad tiene CWE-1204?

MITRE no ha publicado una calificación de probabilidad de explotación para esta debilidad. Trátala como de impacto medio hasta que tu modelo de amenazas demuestre lo contrario.

¿Qué lenguajes o plataformas se ven afectados por CWE-1204?

MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.

¿Cómo puedo prevenir 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…

¿Cómo detecta y corrige Plexicus CWE-1204?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-1204 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.

¿Dónde puedo aprender más sobre CWE-1204?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/1204.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-1204

CWE-330 Padre

Use of Insufficiently Random Values

This vulnerability occurs when an application uses random values that are not sufficiently unpredictable in security-sensitive operations,…

CWE-1241 Hermano

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 Hermano

Insufficient Entropy

This vulnerability occurs when a system's random number generator or algorithm lacks sufficient unpredictability, creating patterns or…

CWE-334 Hermano

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 Hermano

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 Hermano

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 Hermano

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 Hermano

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-329 Hijo

Generation of Predictable IV with CBC Mode

This vulnerability occurs when software uses a predictable or reused Initialization Vector (IV) with Cipher Block Chaining (CBC) mode…

Recursos

Further reading

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