{"id":"CVE-2025-40300","revision":"b1897f73c04f4071a24de6233c092ec3","records":[{"revision":"b1897f73c04f4071a24de6233c092ec3","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2025-40300","aliases":[],"title":"x86/vmscape: Add conditional IBPB mitigation","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/vmscape: Add conditional IBPB mitigation\n\nVMSCAPE is a vulnerability that exploits insufficient branch predictor\nisolation between a guest and a userspace hypervisor (like QEMU). Existing\nmitigations already protect kernel/KVM from a malicious guest. Userspace\ncan additionally be protected by flushing the branch predictors after a\nVMexit.\n\nSince it is the userspace that consumes the poisoned branch predictors,\nconditionally issue an IBPB after a VMexit and before returning to\nuserspace. Workloads that frequently switch between hypervisor and\nuserspace will incur the most overhead from the new IBPB.\n\nThis new IBPB is not integrated with the existing IBPB sites. For\ninstance, a task can use the existing speculation control prctl() to\nget an IBPB at context switch time. With this implementation, the\nIBPB is doubled up: one at context switch and another before running\nuserspace.\n\nThe intent is to integrate and optimize these cases post-embargo.\n\n[ dhansen: elaborate on suboptimal IBPB solution ]","state":0,"publishedAt":"2025-09-11T16:49:24.809+00:00","modifiedAt":"2026-10-15T01:09:08.416+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"arch/x86/include/asm/cpufeatures.h\",\n                        \"arch/x86/include/asm/entry-common.h\",\n                        \"arch/x86/include/asm/nospec-branch.h\",\n                        \"arch/x86/kernel/cpu/bugs.c\",\n                        \"arch/x86/kvm/x86.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"ac60717f9a8d21c58617d0b34274babf24135835\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"c08192b5d6730a914dee6175bc71092ee6a65f14\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"d5490dfa35427a2967e00a4c7a1b95fdbc8ede34\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"15006289e5c38b2a830e1fba221977a27598176c\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"893387c18612bb452336a5881da0d015a7e8f4a2\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"f866eef8d1c65504d30923c3f14082ad294d0e6d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"34e5667041050711a947e260fc9ebebe08bddee5\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"d7ddc93392e4a7ffcccc86edf6ef3e64c778db52\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"459274c77b37ac63b78c928b4b4e748d1f9d05c8\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"510603f504796c3535f67f55fb0b124a303b44c8\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"9c23a90648e831d611152ac08dbcd1283d405e7f\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"15d45071523d89b3fb7372e2135fbd72f6af9506\",\n                            \"lessThan\": \"2f8f173413f1cbf52660d04df92d0069c4306d25\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"c51f1e5f57cca88d8d5894b6fad1638f643a99d0\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"4b3870c343a82cd2df7192cc5149c87205dcc611\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"3.16.57\",\n                            \"lessThan\": \"3.17\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"4.4.168\",\n                            \"lessThan\": \"4.5\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"arch/x86/include/asm/cpufeatures.h\",\n                        \"arch/x86/include/asm/entry-common.h\",\n                        \"arch/x86/include/asm/nospec-branch.h\",\n                        \"arch/x86/kernel/cpu/bugs.c\",\n                        \"arch/x86/kvm/x86.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"4.16\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"4.16\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.244\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.193\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.152\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.106\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.47\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.16.7\",\n                            \"lessThanOrEqual\": \"6.16.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.17\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/ac60717f9a8d21c58617d0b34274babf24135835","https://git.kernel.org/stable/c/c08192b5d6730a914dee6175bc71092ee6a65f14","https://git.kernel.org/stable/c/d5490dfa35427a2967e00a4c7a1b95fdbc8ede34","https://git.kernel.org/stable/c/2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e","https://git.kernel.org/stable/c/15006289e5c38b2a830e1fba221977a27598176c","https://git.kernel.org/stable/c/893387c18612bb452336a5881da0d015a7e8f4a2","https://git.kernel.org/stable/c/f866eef8d1c65504d30923c3f14082ad294d0e6d","https://git.kernel.org/stable/c/34e5667041050711a947e260fc9ebebe08bddee5","https://git.kernel.org/stable/c/d7ddc93392e4a7ffcccc86edf6ef3e64c778db52","https://git.kernel.org/stable/c/459274c77b37ac63b78c928b4b4e748d1f9d05c8","https://git.kernel.org/stable/c/510603f504796c3535f67f55fb0b124a303b44c8","https://git.kernel.org/stable/c/9c23a90648e831d611152ac08dbcd1283d405e7f","https://git.kernel.org/stable/c/2f8f173413f1cbf52660d04df92d0069c4306d25"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-40300","license":"CVE Program Terms of Use","key":"cve-program:CVE-2025-40300","identifiers":["CVE-2025-40300"]},"retained":false,"historicalAffected":[]}],"coverage":[]}