CVE-2024-28956

New Spectre-v2 attack classes have been discovered within CPU architectures that enable self-training exploitation of speculative execution within the same privilege domain. These novel techniques bypass existing hardware and software mitigations, including IBPB, eIBRS, and BHI_NO, by leveraging in-kernel gadgets (potentially accessible via SECCOMP/cBPF), Branch Target Buffer (BTB) aliasing, and direct-to-indirect branch predictor training. While the root cause lies in CPU architectural behavior, the vulnerability manifests through kernel-level speculation paths, allowing attackers to potentially leak sensitive memory.

The "Training Solo" attack classes introduce new self-training methods to exploit Spectre-v2 from within domain isolation implementations. They can be reasonably classified as Moderate severity due to several practical and architectural limitations.

First, these attacks rely heavily on the presence of specific in-kernel or in-hypervisor gadgets, such as history-crafting or disclosure gadgets, which are not universally available and vary across kernel versions and configurations.

Second, the attacks generally require local code execution within the victim domain, meaning they do not expand the threat model beyond existing Spectre-v2 scenarios where attackers already have some degree of execution capability.

Third, the leak rates, while measurable, remain relatively low (1.7–17 KB/s) and demand sustained access and stability to extract meaningful information. So their limited practical exploitability makes them a moderate, not critical, threat in real-world settings.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.