The Linux kernel atmel‑sha204a driver mismanaged the entropy buffer, causing the blocking and non‑blocking RNG paths to return primarily zeroed data. This flaw is a classic instance of CWE‑331: Improper Entropy Generation. As a result, /dev/hwrng delivers insufficient high‑quality randomness, weakening cryptographic key generation, tokens, or any protocol that depends on the hardware random source. The flaw does not provide direct code execution or denial‑of‑service but reduces the unpredictability of the system’s cryptographic operations.

All Linux kernel releases that incorporate the atmel_sha204a driver before the commit that fixes the buffer handling. The issue was validated on Atmel SHA204A devices and applies to any system using that hardware random number generator within the kernel.

The CVSS score is 5.5, and the EPSS score is < 1%. The vulnerability is local; an attacker with physical or local access could observe the deficient randomness and potentially weaken crypto processes. The vulnerability is not listed in the CISA KEV catalog, suggesting limited evidence of active exploitation yet the correctness of entropy remains critical. The attack vector is inferred to be local/device‑based, not remote. Mitigating steps such as updating the kernel or disabling the defective RNG path lower the attack likelihood.