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CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

BaseLikelihood of exploit: Medium

The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.

When a non-cryptographic PRNG is used in a cryptographic context, it can expose the cryptography to certain types of attacks. Often a pseudo-random number generator (PRNG) is not designed for cryptography. Sometimes a mediocre source of randomness is sufficient or preferable for algorithms that use random numbers. Weak generators generally take less processing power and/or do not use the precious, finite, entropy sources on a system. While such PRNGs might have very useful features, these same features could be used to break the cryptography.

Consequences

  • Access Control: Bypass Protection Mechanism

How to prevent it

  • Implementation: Use functions or hardware which use a hardware-based random number generation for all crypto. This is the recommended solution. Use CyptGenRandom on Windows, or hw_rand() on Linux.

Recent advisories

  • GHSA-mfj3-87qq-382v — AsyncHttpClient: Digest authentication cnonce generated with a non-cryptographic random source
  • PYSEC-2026-3745 — openssl_encrypt before 1.4.0 imports Python's non-cryptographic 'random' module (Mersenne Twister PRNG) at line 15 of openssl_encrypt/modules/pqc.py.
  • GHSA-jxw3-mjmx-3pqm — Langflow: Weak Fernet Key via random.seed()
  • GHSA-vfgx-5q85-58q3 — openssl-encrypt has non-cryptographic PRNG used for steganography pixel selection
  • GHSA-82vr-5769-6358 — Ethyca Fides Cryptographically Weak Generation of One-Time Codes for Identity Verification
  • GHSA-c4r2-3f9r-rwp8 — Magento 2 Community Weak PRNG
  • GHSA-8v9h-m7pj-hx7c — Magento 2 Community Edition Weak PRNG
  • GHSA-2w26-gmqm-mc5p — Magento 2 Community Cryptographic Flaw
  • GHSA-vrgh-5w3c-ggf8 — showdoc is vulnerable to Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
  • GHSA-j85q-whc9-g4p9 — Use of Cryptographically Weak Pseudo-Random Number Generator in showdoc
  • GHSA-rmw5-xpg9-jr29 — Use of Cryptographically Weak Pseudo-Random Number Generator in Rclone
  • GHSA-gwf7-vfjf-wf6x — matrix-sydent and matrix-synapse Use Cryptographically Weak PRNG

All advisories for CWE-338

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