CWE-1204 Base Incomplet

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…

Définition

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.
Impact réel

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

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

  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].

Exemple de code vulnérable

Vulnerable C

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

Vulnérable 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);
Exemple de code sécurisé

Secure pseudo

Sécurisé 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.
Liste de contrôle de prévention

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].
Signaux de détection

How to detect CWE-1204

SAST High

Exécuter une analyse statique (SAST) sur le code source à la recherche du motif non sécurisé dans le flux de données.

DAST Moderate

Exécuter des tests de sécurité applicative dynamique (DAST) contre le point de terminaison en ligne.

Runtime Moderate

Surveiller les journaux runtime pour détecter des traces d'exception inhabituelles, des entrées malformées ou des tentatives de contournement d'autorisation.

Code review Moderate

Revue de code : signaler tout nouveau code qui traite les entrées de cette surface sans utiliser les helpers du framework validés.

Correction automatique Plexicus

Plexicus détecte automatiquement CWE-1204 et ouvre une PR de correction en moins de 60 secondes.

Codex Remedium analyse chaque commit, identifie cette faiblesse précise et livre une pull request prête à être relue avec le correctif. Pas de tickets. Pas de transferts.

Obtenir une démo Essayer Plexicus gratuitement
Questions fréquentes

Frequently asked questions

Qu'est-ce que 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.

Quelle est la gravité de CWE-1204 ?

MITRE n'a pas publié de note de probabilité d'exploitation pour cette faiblesse. Traitez-la comme un impact moyen jusqu'à ce que votre modèle de menace prouve le contraire.

Quels langages ou plateformes sont affectés par CWE-1204 ?

MITRE n'a pas spécifié les plateformes affectées pour ce CWE — il peut s'appliquer à la plupart des stacks applicatives.

Comment puis-je prévenir 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…

Comment Plexicus détecte et corrige CWE-1204 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-1204 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.

Où puis-je en savoir plus sur CWE-1204 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/1204.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-1204

CWE-330 Parent

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 Frère

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 Frère

Insufficient Entropy

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

CWE-334 Frère

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 Frère

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 Frère

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 Frère

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 Frère

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 Enfant

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…

Ressources

Further reading

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