Spectre branch target injection from VM guests ("VMScape")

CVE / CVSS

Base scores are looked up from NVD or, if NVD has none yet, the CVE record. Proxmox itself does not publish CVSS scores. “Actively exploited” comes from the CISA KEV catalog, EPSS (probability of exploitation in the next 30 days) from FIRST.

Details

Incomplete branch predictor isolation mechanisms allow exploitation of branch prediction across hypervisor/guest context switches, potentially leaking secrets from the host userspace or other guests by an attacker with control over a VM.

Fixed in

For Debian Trixie based releases, like Proxmox VE 9, Proxmox Backup Server 4 or Proxmox Datacenter Manager Beta:

• Package proxmox-kernel-6.14.11-2-pve-signed in version 6.14.11-2

For Debian Bookworm based releases, like Proxmox VE 8, Proxmox Backup Server 3 or Proxmox Mail Gateway 8:

• Package proxmox-kernel-6.14.8-3-bpo12-pve-signed in version 6.14.8-3~bpo12+1

• Package proxmox-kernel-6.8.12-15-pve-signed in version 6.8.12-15

References

• CVE-2025-40300 (opens in a new tab)

• https://comsec.ethz.ch/research/mic...ch-predictor-isolation-in-cloud-environments/ (opens in a new tab)