- AMD Zen 5 chips have a flaw in RDSEED that risks cryptographic key integrity
- A faulty RDSEED can return zeros, allowing attackers to reconstruct private keys and break encryption.
- AMD recommends using 64-bit RDSEED or software alternatives
Some AMD processors, including those built on the latest Zen 5 architecture, carry a critical vulnerability that affects cryptographic operations and thus endangers the integrity of protected data.
In a security bulletin, AMD detailed a flaw titled “AMD-SB-7055,” describing it as a vulnerability in the RDSEED hardware random number generator.
On affected chips, both 16-bit and 32-bit forms of the RDSEED instruction may return “0” at a rate that is not entirely random and still call the process a success. In theory, if a company operates a server that generates cryptographic keys to encrypt customer data, and the software running on that server uses RDSEED instructions to obtain random numbers directly from the chip, the instruction might return only zeros.
Fixes and mitigations
Although none of this is obviously due to chance, it would still indicate that the operation was successful, without triggering any alarm signals.
As a result, attackers who obtain one of the public keys can mathematically reconstruct or guess the private key, breaking encryption or impersonating the company, meaning encrypted customer records, API tokens, or even software update signatures could be tampered with or decrypted.
Mitigation and fixes are already in the works. By January 2026, according to the processor, most should have been mitigated.
Patches for AMD’s mainstream Zen 5 chips, including the Ryzen 9000, AI Max 300, Threadripper 9000, and Ryzen Z2 series, will be released on November 25.
AMD added that it should soon have the necessary AGESA microcode updates to resolve this issue on all Zen 5 processors.
If you’re using chips that don’t yet have functional mitigation, AMD recommends reverting to its unaffected 64-bit form of RDSEED, or switching to a software rollback until release.
Via Tom’s material
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