CVE-2025-40300

Summary

In the Linux kernel, the following vulnerability has been resolved:

x86/vmscape: Add conditional IBPB mitigation

VMSCAPE is a vulnerability that exploits insufficient branch predictor isolation between a guest and a userspace hypervisor (like QEMU). Existing mitigations already protect kernel/KVM from a malicious guest. Userspace can additionally be protected by flushing the branch predictors after a VMexit.

Since it is the userspace that consumes the poisoned branch predictors, conditionally issue an IBPB after a VMexit and before returning to userspace. Workloads that frequently switch between hypervisor and userspace will incur the most overhead from the new IBPB.

This new IBPB is not integrated with the existing IBPB sites. For instance, a task can use the existing speculation control prctl() to get an IBPB at context switch time. With this implementation, the IBPB is doubled up: one at context switch and another before running userspace.

The intent is to integrate and optimize these cases post-embargo.

[ dhansen: elaborate on suboptimal IBPB solution ]

Affected Software

VendorProductVersion RangeStatus
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < ac60717f9a8d21c58617d0b34274babf24135835affected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < c08192b5d6730a914dee6175bc71092ee6a65f14affected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < d5490dfa35427a2967e00a4c7a1b95fdbc8ede34affected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < 2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6eaffected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < 15006289e5c38b2a830e1fba221977a27598176caffected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < 893387c18612bb452336a5881da0d015a7e8f4a2affected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < f866eef8d1c65504d30923c3f14082ad294d0e6daffected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < 34e5667041050711a947e260fc9ebebe08bddee5affected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < d7ddc93392e4a7ffcccc86edf6ef3e64c778db52affected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < 459274c77b37ac63b78c928b4b4e748d1f9d05c8affected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < 510603f504796c3535f67f55fb0b124a303b44c8affected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < 9c23a90648e831d611152ac08dbcd1283d405e7faffected
LinuxLinux15d45071523d89b3fb7372e2135fbd72f6af9506 < 2f8f173413f1cbf52660d04df92d0069c4306d25affected
LinuxLinuxc51f1e5f57cca88d8d5894b6fad1638f643a99d0affected
LinuxLinux4b3870c343a82cd2df7192cc5149c87205dcc611affected
LinuxLinux3.16.57 < 3.17affected
LinuxLinux4.4.168 < 4.5affected
LinuxLinux4.16affected
LinuxLinux0 < 4.16unaffected
LinuxLinux5.10.244 <= 5.10.*unaffected
LinuxLinux5.15.193 <= 5.15.*unaffected
LinuxLinux6.1.152 <= 6.1.*unaffected
LinuxLinux6.6.106 <= 6.6.*unaffected
LinuxLinux6.12.47 <= 6.12.*unaffected
LinuxLinux6.16.7 <= 6.16.*unaffected
LinuxLinux6.17 <= *unaffected

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

Additional References

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References