StackWarp vulnerability exposes AMD SEV-SNP virtual machines

As outlined in The Register, a newly discovered vulnerability named StackWarp poses a significant risk to virtual machines utilizing AMD's Secure Encrypted Virtualization-Secure Nested Paging (SEV-SNP) technology. Computer scientists have identified a flaw that could allow malicious insiders to access sensitive data within these protected virtual environments.

The StackWarp vulnerability (CVE-2025-29943) exploits a microarchitectural weakness in AMD Zen CPUs, particularly when Simultaneous Multithreading (SMT) is enabled. By manipulating a specific control bit, an attacker with host server access can interfere with the stack pointer within a virtual machine. This interference can lead to the recovery of cryptographic private keys, bypass of OpenSSH password authentication, and privilege escalation. The attack targets the integrity guarantees of SEV-SNP, which is designed to isolate virtual machines from the hypervisor, a feature crucial for cloud providers offering confidential virtual machines.

While AMD has released patches and designated the issue as low severity, StackWarp highlights the ongoing challenges in ensuring complete isolation of virtual computing resources. Users are advised to apply the available patches to mitigate the risk of such attacks, which could undermine the security promises of confidential computing environments.

Source: The Register