AMD CPU users beware - this security flaw could spill all your secrets

• CISPA researchers uncover AMD CPU flaw “StackWarp” breaking confidential VM protections
• Vulnerability enables RCE, privilege escalation, and theft of private keys in Zen processors
• AMD released patch (CVE-2025-29943), rated low severity, requiring host-level access to exploit

A newly discovered vulnerability in AMD chips allows malicious actors to perform remote code execution (RCE) and privilege escalation in virtual machines.

Cybersecurity researchers from the CISPA Helmholtz Center for Information Security in Germany detailed a vulnerability they named StackWarp, a hardware vulnerability in AMD CPUs that breaks the protections of confidential virtual machines, by manipulating how the processor tracks the stack, and letting a malicious insider or hypervisor change program flow or read sensitive data inside a protected VM.

As a result, malicious actors can recover private keys, and run code with high privileges, even though the VM’s memory was supposed to be secure.

Silver lining

StackWarp was said to impact AMD Zen processors, 1 through 5, with the researchers demonstrating the impact in multiple scenarios. In one instance, they were able to reconstruct an RSE-2048 private key, while in another - bypassed OpenSSH password authentication.

The silver lining in the report is the fact that the malicious actor first needs privileged control over the host server running the virtual machines. That means the vulnerability can be exploited by either malicious insiders, cloud providers, or highly sophisticated threat actors with prior access.

This significantly shrinks the number of potential attackers, but it still highlights how AMD’s SEV-SNP, designed to encrypt VM memory, can be weakened and compromised.

“These findings demonstrate that CVM execution integrity—the very defense SEV-SNP aims to offer—can be effectively broken: Confidential keys and passwords can be stolen, attackers can impersonate legitimate users or gain persistent control of the system, and isolation between guest VMs and the host or other VMs can no longer be relied upon,” it was said in the report.

AMD acknowledged the findings and has released a patch, which the bug now tracked as CVE-2025-29943 and was given a low severity score (3.2/10).

Via The Register

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