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 ]
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 ]
Metrics
Affected Vendors & Products
| Vendors | Products |
|---|---|
| Linux |
|
No data.
No data.
OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.
| Vendors | Products |
|---|---|
| Linux |
|
Advisories
| Source | ID | Title |
|---|---|---|
 Debian DLA |
DLA-4327-1 | linux security update |
| Debian DLA |
DLA-4328-1 | linux-6.1 security update |
 Debian DSA |
DSA-6008-1 | linux security update |
| Debian DSA |
DSA-6009-1 | linux security update |
 EUVD |
EUVD-2025-28976 | 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 ] |
 Ubuntu USN |
USN-7850-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-7853-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-7853-2 | Linux kernel (FIPS) vulnerabilities |
| Ubuntu USN |
USN-7854-1 | Linux kernel (KVM) vulnerabilities |
| Ubuntu USN |
USN-7860-1 | Linux kernel vulnerability |
| Ubuntu USN |
USN-7861-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-7862-1 | Linux kernel vulnerability |
| Ubuntu USN |
USN-7863-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-7860-2 | Linux kernel (Real-time) vulnerability |
| Ubuntu USN |
USN-7861-2 | Linux kernel (Real-time) vulnerabilities |
| Ubuntu USN |
USN-7864-1 | Linux kernel (GCP and GKE) vulnerabilities |
| Ubuntu USN |
USN-7860-3 | Linux kernel (FIPS) vulnerability |
| Ubuntu USN |
USN-7860-4 | Linux kernel (Real-time) vulnerability |
| Ubuntu USN |
USN-7853-3 | Linux kernel (Azure) vulnerabilities |
| Ubuntu USN |
USN-7862-2 | Linux kernel vulnerability |
| Ubuntu USN |
USN-7865-1 | Linux kernel (FIPS) vulnerabilities |
| Ubuntu USN |
USN-7861-3 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-7862-3 | Linux kernel (Xilinx ZynqMP) vulnerability |
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Fri, 14 Nov 2025 10:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
Mon, 03 Nov 2025 18:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
Mon, 15 Sep 2025 07:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
Fri, 12 Sep 2025 08:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Linux
Linux linux Kernel |
|
| Vendors & Products |
Linux
Linux linux Kernel |
Fri, 12 Sep 2025 00:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-402 | |
| References |
| |
| Metrics |
threat_severity
|
cvssV3_1
|
Thu, 11 Sep 2025 17:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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 ] | |
| Title | x86/vmscape: Add conditional IBPB mitigation | |
| References |
|
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-11-14T10:04:19.936Z
Reserved: 2025-04-16T07:20:57.185Z
Link: CVE-2025-40300
Vulnrichment
No data.
NVD
Status : Awaiting Analysis
Published: 2025-09-11T17:15:45.680
Modified: 2025-11-14T10:15:56.550
Link: CVE-2025-40300
Redhat
OpenCVE Enrichment
Updated: 2025-09-12T08:02:51Z