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High

Linux kernel KVM x86 race condition in __get_sregs2() PDPTR handling

IdentifiersCVE-2026-43214CWE-362

CVE-2026-43214 is a flaw in the Linux kernel KVM x86 subsystem in the __get_sregs2() path when reading PDPTR registers. Reading PDPTRs can trigger guest-memory access through the call chain kvm_pdptr_read() -> svm_cache_reg() -> load_pdptrs() -> kvm_vcpu_read_guest_page() -> kvm_vcpu_gfn_to_memslot(). In the vulnerable path, kvm_vcpu_gfn_to_memslot() dereferences memslots via __kvm_memslots(), which uses srcu_dereference_check() and requires either kvm->srcu or kvm->slots_lock to be held. However, only vcpu->mutex was held. The issue was resolved by adding SRCU read-side protection around the PDPTR read path in __get_sregs2(). The bug was identified by the Linux Verification Center using Syzkaller.

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Impact

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The flaw can lead to unsafe concurrent access to KVM memslot state during guest-memory lookup from the __get_sregs2() ioctl path. The provided material specifically shows lockdep-detected suspicious RCU usage and an upstream fix adding the missing SRCU protection. Based on the supplied CVSS assessments, successful exploitation may affect confidentiality, integrity, and availability of the host kernel/KVM context, but the exact practical exploitation consequences beyond the race and invalid synchronization are not further described in the provided content.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure by limiting local access to KVM management interfaces and restricting who can invoke KVM vCPU ioctls against running VMs, since the issue is in a local KVM ioctl path and requires privileges to interact with a guest vCPU. No specific workaround other than applying the fixed kernel is provided in the supplied content.

Remediation

Patch, then assume compromise.

Apply a kernel update that includes the upstream fix for CVE-2026-43214, which adds SRCU read-side protection for PDPTR reads in __get_sregs2(). The content references stable fixes including commits f621ca24f9f489e226e22560761b04884984133b, 708e20c66b2761d878a2bc3c7534e7f814e4dec5, 9f2bfea51151dfbb24b52f452eb3d5f5fe0e506e, 57536ff0a6bd69a5808d682925202babdb5ddc13, b33f8d816950b10e7879cd8ffd7ae4b649ada4db, and 95d848dc7e639988dbb385a8cba9b484607cf98c. For SUSE environments, install the relevant released kernel updates/advisories that include the fix and reboot into the updated kernel.
PUBLIC EXPLOITS

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VALID 0 / 0 TOTALView more in app

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LinuxLinux Kerneloperating_system

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