AMD has confirmed a hardware defect in the RDSEED instruction on its new Zen 5 processors, cataloged as AMD-SB-7055 and assigned CVE-2025-62626. The company reports that the 16-bit and 32-bit forms of RDSEED can return zero values, which may be mistakenly interpreted as a successful entropy read. The 64-bit form is unaffected. AMD rates the issue as high severity and suggests short-term software workarounds: prioritize using the 64-bit RDSEED path where possible, mask RDSEED from software discovery, or treat a zero return as a failure and retry. Firmware and microcode updates are being rolled out to OEMs. AMD's advisory provides product-family target dates, such as AGESA TurinPI 1.0.0.8 for EPYC 9005, with a target date of November 14, 2025, and consumer families targeted for late November 2025. Users should install vendor BIOS/microcode updates when available and consider regenerating any sensitive keys created on unpatched systems.

RDSEED is a low-level instruction that supplies entropy used for cryptographic keys and other security functions. When it returns predictable values without detection, newly generated keys or nonces may be weaker than intended. According to AMD, the problem affects the 16-bit and 32-bit forms of RDSEED, while the 64-bit form does not appear to be impacted. The company is distributing firmware and platform updates to correct the issue, but until those updates are applied, the recommended interim measures are straightforward: prefer the 64-bit RDSEED path where possible, prevent software from discovering or using the affected RDSEED forms, or treat a zero result as a failure and retry. Once updates become available, users should install them promptly and consider regenerating any sensitive keys created on unpatched systems.