{"id":"CVE-2026-98466","state":"PUBLISHED","title":"KVM: arm64: Transfer the hyp stack pages out of the host stage-2","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Transfer the hyp stack pages out of the host stage-2\n\nfix_host_ownership() walks only the linear-map alias of each memblock\nregion, and the per-CPU hyp stack, mapped in the private VA range for\nits guard page, has none.\n\nWalk each stack's VA range with the same walker.","publishedAt":"2026-10-18T15:15:18.414Z","updatedAt":"2026-10-24T14:08:58.562Z","severity":{"score":8.2,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1a919b17ef012ca0572bae759c27e5ea02bfb47f","status":"affected","lessThan":"e5dd2a91a7ae3a276e6d79806127e923936e241b","versionType":"git"},{"version":"1a919b17ef012ca0572bae759c27e5ea02bfb47f","status":"affected","lessThan":"22df195bff84300a3f04813d6148765c77ac565a","versionType":"git"},{"version":"1a919b17ef012ca0572bae759c27e5ea02bfb47f","status":"affected","lessThan":"3a8c562892b96f35bba1e00d5e455a15963bbb92","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/hyp/nvhe/setup.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.19","versionType":"semver"},{"version":"6.18.55","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.9","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/hyp/nvhe/setup.c"]}],"references":["https://git.kernel.org/stable/c/e5dd2a91a7ae3a276e6d79806127e923936e241b","https://git.kernel.org/stable/c/22df195bff84300a3f04813d6148765c77ac565a","https://git.kernel.org/stable/c/3a8c562892b96f35bba1e00d5e455a15963bbb92"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98466.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98466","state":"PUBLISHED","datePublished":"2026-10-18T15:15:18.414Z","dateUpdated":"2026-10-24T14:08:58.562Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.351Z"},"containers":{"cna":{"title":"KVM: arm64: Transfer the hyp stack pages out of the host stage-2","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Transfer the hyp stack pages out of the host stage-2\n\nfix_host_ownership() walks only the linear-map alias of each memblock\nregion, and the per-CPU hyp stack, mapped in the private VA range for\nits guard page, has none.\n\nWalk each stack's VA range with the same walker."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1a919b17ef012ca0572bae759c27e5ea02bfb47f","status":"affected","lessThan":"e5dd2a91a7ae3a276e6d79806127e923936e241b","versionType":"git"},{"version":"1a919b17ef012ca0572bae759c27e5ea02bfb47f","status":"affected","lessThan":"22df195bff84300a3f04813d6148765c77ac565a","versionType":"git"},{"version":"1a919b17ef012ca0572bae759c27e5ea02bfb47f","status":"affected","lessThan":"3a8c562892b96f35bba1e00d5e455a15963bbb92","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/hyp/nvhe/setup.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.19","versionType":"semver"},{"version":"6.18.55","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.9","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/hyp/nvhe/setup.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e5dd2a91a7ae3a276e6d79806127e923936e241b"},{"url":"https://git.kernel.org/stable/c/22df195bff84300a3f04813d6148765c77ac565a"},{"url":"https://git.kernel.org/stable/c/3a8c562892b96f35bba1e00d5e455a15963bbb92"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H","baseScore":8.2,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The local `module_init(kvm_arm_init)` path reaches `init_hyp_mode()` → `kvm_hyp_init_protection()` → `do_pkvm_init()` → `handle___pkvm_init()` → `__pkvm_init()` → `__pkvm_init_finalise()` → patched `fix_host_ownership()`. Exploitation accesses the omitted stack pages through host direct-map aliases; no wire or guest message supplies causal data.\nAC:L - With `kvm-arm.mode=protected`, the omitted pages retain host-owned state, so `handle_host_mem_abort()` → `host_stage2_idmap()` deterministically installs `PKVM_HOST_MEM_PROT` RWX mappings. The attacker controls the stack access and a following HVC; no race or external condition is required.\nPR:H - `/dev/kvm` ioctls only cause EL2 to use the stack; they do not expose `kvm_arm_hyp_stack_base` or its PFN. Writing the kernel direct-map alias requires control of host EL1 through real host-administrative privilege, unavailable through user namespaces.\nUI:N - After pKVM initialization, the host attacker can access the retained direct-map alias and invoke an HVC or `KVM_RUN` to make EL2 use the corrupted stack. No action by another user is required.\nS:C - The missing `host_stage2_set_owner_locked(..., PKVM_ID_HYP)` operation lets the host EL1 authority access the protected EL2 stack, crossing the stage-2 boundary that isolates the hypervisor and protected VMs.\nC:H - The host can read live EL2 stack contents, including saved registers and pointers. Its simultaneous write access to stack control data can hijack EL2 execution and expose hypervisor or protected-VM memory.\nI:H - The host can overwrite the active stack used by `__host_exit()` and `handle_trap()`, including saved frame and return state. Control-flow corruption at EL2 can modify hypervisor ownership metadata and protected-VM memory.\nA:H - Corrupting the per-CPU stack consumed on every host-to-EL2 trap can produce invalid returns or hypervisor faults, crashing the hypervisor and consequently the host or its protected VMs."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-24T14:08:58.562Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.18.55"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"7.2.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}