CVE-2025-40300 (GCVE-0-2025-40300)
Vulnerability from cvelistv5
Published
2025-09-11 16:49
Modified
2025-09-15 06:47
Severity ?
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 ]
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/15006289e5c38b2a830e1fba221977a27598176c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2f8f173413f1cbf52660d04df92d0069c4306d25
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/34e5667041050711a947e260fc9ebebe08bddee5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/459274c77b37ac63b78c928b4b4e748d1f9d05c8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/510603f504796c3535f67f55fb0b124a303b44c8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/893387c18612bb452336a5881da0d015a7e8f4a2
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9c23a90648e831d611152ac08dbcd1283d405e7f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ac60717f9a8d21c58617d0b34274babf24135835
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c08192b5d6730a914dee6175bc71092ee6a65f14
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d5490dfa35427a2967e00a4c7a1b95fdbc8ede34
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d7ddc93392e4a7ffcccc86edf6ef3e64c778db52
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f866eef8d1c65504d30923c3f14082ad294d0e6d
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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          "value": "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 ]"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40300",
    "datePublished": "2025-09-11T16:49:24.809Z",
    "dateReserved": "2025-04-16T07:20:57.185Z",
    "dateUpdated": "2025-09-15T06:47:56.333Z",
    "state": "PUBLISHED"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2025-40300\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-09-11T17:15:45.680\",\"lastModified\":\"2025-09-15T15:22:38.297\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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 ]\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/15006289e5c38b2a830e1fba221977a27598176c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/2f8f173413f1cbf52660d04df92d0069c4306d25\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/34e5667041050711a947e260fc9ebebe08bddee5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/459274c77b37ac63b78c928b4b4e748d1f9d05c8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/510603f504796c3535f67f55fb0b124a303b44c8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/893387c18612bb452336a5881da0d015a7e8f4a2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9c23a90648e831d611152ac08dbcd1283d405e7f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ac60717f9a8d21c58617d0b34274babf24135835\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c08192b5d6730a914dee6175bc71092ee6a65f14\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d5490dfa35427a2967e00a4c7a1b95fdbc8ede34\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d7ddc93392e4a7ffcccc86edf6ef3e64c778db52\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f866eef8d1c65504d30923c3f14082ad294d0e6d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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