CVE-2025-40300x86/vmscape: Add conditional IBPB mitigation
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 15, 2026
- First seen by InfoSec Signals
- Oct 15, 2026
Affected products
Linux Linux linux:linux (from the name) | from 15d45071523d89b3fb7372e2135fbd72f6af9506 before ac60717f9a8d21c58617d0b34274babf24135835; from 15d45071523d89b3fb7372e2135fbd72f6af9506 before c08192b5d6730a914dee6175bc71092ee6a65f14; from 15d45071523d89b3fb7372e2135fbd72f6af9506 before d5490dfa35427a2967e00a4c7a1b95fdbc8ede34; 15d45071523d89b3fb7372e2135fbd72f6af9506 builds before 2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e; from 15d45071523d89b3fb7372e2135fbd72f6af9506 before 15006289e5c38b2a830e1fba221977a27598176c; from 15d45071523d89b3fb7372e2135fbd72f6af9506 before 893387c18612bb452336a5881da0d015a7e8f4a2; from 15d45071523d89b3fb7372e2135fbd72f6af9506 before f866eef8d1c65504d30923c3f14082ad294d0e6d; from 15d45071523d89b3fb7372e2135fbd72f6af9506 before 34e5667041050711a947e260fc9ebebe08bddee5; and 9 more ranges | CNA record |
Siemens SIMATIC CN 4100 siemens:simatic_cn_4100 (from the name) | before V5.0 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
linux linux_kernel linux:linux_kernel | from 3.16.57 before 3.17; from 4.4.168 before 4.5; from 4.16 before 5.10.244; from 5.11 before 5.15.193; from 5.16 before 6.1.152; from 6.2 before 6.6.106; from 6.7 before 6.12.47; from 6.13 before 6.16.7; and 5 more ranges | NVD |
debian debian_linux debian:debian_linux | 11.0 | NVD |
References
- https://git.kernel.org/stable/c/ac60717f9a8d21c58617d0b34274babf24135835patch
- https://git.kernel.org/stable/c/c08192b5d6730a914dee6175bc71092ee6a65f14patch
- https://git.kernel.org/stable/c/d5490dfa35427a2967e00a4c7a1b95fdbc8ede34patch
- https://git.kernel.org/stable/c/2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6epatch
- https://git.kernel.org/stable/c/15006289e5c38b2a830e1fba221977a27598176cpatch
- https://git.kernel.org/stable/c/893387c18612bb452336a5881da0d015a7e8f4a2patch
- https://git.kernel.org/stable/c/f866eef8d1c65504d30923c3f14082ad294d0e6dpatch
- https://git.kernel.org/stable/c/34e5667041050711a947e260fc9ebebe08bddee5patch
- https://git.kernel.org/stable/c/d7ddc93392e4a7ffcccc86edf6ef3e64c778db52patch
- https://git.kernel.org/stable/c/459274c77b37ac63b78c928b4b4e748d1f9d05c8patch
- https://git.kernel.org/stable/c/510603f504796c3535f67f55fb0b124a303b44c8patch
- https://git.kernel.org/stable/c/9c23a90648e831d611152ac08dbcd1283d405e7fpatch
- https://git.kernel.org/stable/c/2f8f173413f1cbf52660d04df92d0069c4306d25patch
- http://www.openwall.com/lists/oss-security/2025/11/14/3mailing-list
- http://www.openwall.com/lists/oss-security/2025/11/14/4mailing-list
- http://www.openwall.com/lists/oss-security/2025/11/14/6mailing-list
- http://www.openwall.com/lists/oss-security/2025/11/17/2mailing-list
- http://www.openwall.com/lists/oss-security/2025/11/17/3mailing-list
- https://lists.debian.org/debian-lts-announce/2025/10/msg00007.htmlthird-party-advisory
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlthird-party-advisory
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-032379.html
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.