- AMD Zen 5 chips have a flaw in RDSEED that risks cryptographic key integrity
- Defective RDSEED can return nulls, allowing attackers to reconstruct private keys and break encryption
- AMD advises against 64-bit RDSEED or software alternatives
Some AMD processors, including those built on the latest Zen 5 architecture, have a critical vulnerability that affects cryptographic operations and thus puts the integrity of protected data at serious risk.
In a security bulletin, AMD described a bug labeled “AMD-SB-7055” and described it as a vulnerability in the RDSEED hardware-based random number generator.
On affected chips, the 16-bit and 32-bit form of the RDSEED instruction can return “0” at a rate that is not completely random, while at the same time marking the process as successful. In theory, if a company runs a server that generates cryptographic keys to encrypt customer data, and the software running on that server uses RDSEED instructions to get random numbers directly from the chip, the instruction could return all zeros.
Patches and fixes
While obviously not completely random, it would still signal that it was successful and raise absolutely no red flags.
As a result, attackers who obtain one of the public keys can mathematically reconstruct or guess the private key, break encryption or impersonate the company, meaning that encrypted customer registrations, API tokens or even software update signatures can be forged or decrypted.
Mitigations and patches are already underway. By January 2026, depending on the CPU, most of it should have been mitigated.
Patches for AMD’s consumer Zen 5 chips, including the Ryzen 9000 series, AI Max 300 series, Threadripper 9000 series, and Ryzen Z2 series, will be released on November 25.
AMD added that it should have the necessary AGESA microcode updates “soon” to fix this issue across all Zen 5 CPUs.
If you’re running chips that don’t yet have a working limitation, AMD recommends that you switch back to its unaffected 64-bit form of RDSEED or move to a software bug until it’s released.
Via Tom’s hardware
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