DEBIAN-CVE-2025-40300

Advisory lineage Upstream: 1 Downstream: 4
Upstream
CVE-2025-40300
Published: 11 Sept 2025, 17:15
Last modified:28 Apr 2026, 20:30

Vulnerability Summary

Overall Risk (default)
low
22/100
CVSS Score
5.5 MEDIUM
3.1 (osv_debian)
EPSS Score
No data
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

11 Sept 2025, 17:15
Published
Vulnerability first disclosed
28 Apr 2026, 20:30
Last Modified
Vulnerability information updated

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 ]

CVSS Metrics

  • v3.1•MEDIUM•Score: 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Systems

  • debian•linux

    < 5.10.244-1 | < 6.1.153-1 | < 6.12.48-1 | < 6.16.7-1

  • debian•linux-6.1

    < 6.1.153-1~deb11u1

References (1)