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Insecure generation of random numbers - Static IV

Description

The application uses static, hardcoded values for initialization vectors. By knowing initialization vectors an attacker could perform a reverse engineering attack to predict the random values that should remain as secrets.

Impact

Predict random values to craft new attack vectors.

Recommendation

Generate initialization vectors randomly using mechanisms with secure randomness and high entropy.

Threat

Authenticated attacker from the Internet with access to the source code.

Expected Remediation Time

⌚ 30 minutes.

Score

Default score using CVSS 3.1. It may change depending on the context of the vulnerability.

Base

  • Attack vector: N
  • Attack complexity: H
  • Privileges required: L
  • User interaction: N
  • Scope: U
  • Confidentiality: L
  • Integrity: N
  • Availability: N

Temporal

  • Exploit code madurity: P
  • Remediation level: U
  • Report confidence: C

Result

  • Vector string: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N/E:P/RL:U/RC:C
  • Score:
    • Base: 3.1
    • Temporal: 3.0
  • Severity:
    • Base: Low
    • Temporal: Low

Code Examples

Compliant code

The application includes secure encryption algorithms

from Crypto import Random
from Crypto.Cipher import AES
from Crypto.Util.Padding import paddef encrypt(value, key):
value = value.encode('ascii')
iv = Random.new().read(AES.block_size)
cipher = AES.new(key, AES.MODE_CBC, iv)
ciphertext = cipher.encrypt(pad(bytes(value, encoding='utf8'), size))
return iv + ciphertext

Non compliant code

The application uses insecure encryption algorithms

from Crypto import Random
from Crypto.Cipher import AES
from Crypto.Util.Padding import paddef encrypt(value, key):
value = value.encode('ascii')
iv = "HardCodedValue"
cipher = AES.new(key, AES.MODE_CBC, iv)
ciphertext = cipher.encrypt(pad(bytes(value, encoding='utf8'), size))
return iv + ciphertext

Requirements

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