{"id":"DEBIAN-CVE-2026-68093","details":"In the Linux kernel, the following vulnerability has been resolved:  KVM: SVM: Bump asid_generation on CPU online to avoid ASID collision after hotplug  If a vCPU stays scheduled out (or blocked) while the last pCPU it ran on goes through a hotplug cycle (online-\u003eoffline-\u003eonline), and the vCPU then resumes execution on the same pCPU, then it is possible for it to run with an ASID that has now been assigned to a different vCPU, resulting in stale TLB translations being used.  svm_enable_virtualization_cpu() resets asid_generation to 1 and sets next_asid to max_asid + 1 on every CPU online event, including hotplug cycles.  Because next_asid starts beyond the pool boundary, the first call to new_asid() after an online event always wraps the pool, incrementing asid_generation to 2 and assigning ASIDs starting from min_asid.  Consider two vCPUs from different VMs, vCPU-A pinned to CPU-X holding asid_generation=2 and ASID=N from before the hotplug event:    1. CPU-X goes offline and back online: asid_generation resets to 1,      next_asid = max_asid + 1.    2. One or more vCPUs migrate to CPU-X and call new_asid(), wrapping      the pool and consuming ASIDs starting from min_asid.  Eventually      vCPU-B from a different VM is assigned asid_generation=2, ASID=N      — the same ASID that vCPU-A held before the hotplug.    3. vCPU-A enters pre_svm_run() on CPU-X: current_vmcb-\u003ecpu is      unchanged so the migration branch is skipped.  Its saved      asid_generation=2 matches sd-\u003easid_generation=2, so the generation      check silently passes and vCPU-A continues running with ASID=N —      the same ASID just freshly assigned to vCPU-B.  Both vCPUs from different VMs now run on CPU-X with the same ASID, causing them to share NPT TLB entries and producing stale translations.  The collision manifests as a KVM internal error (Suberror: 1, emulation failure).  The NPT page fault reports a faulting GPA far outside the VM's physical memory range — a sign of stale TLB translations being used.  KVM falls back to instruction emulation, which fails on FPU/XSave instructions (XRSTOR, STMXCSR) that the emulator does not implement.  Fix this by incrementing asid_generation instead of resetting it to 1 in svm_enable_virtualization_cpu().  On module load, asid_generation starts at 0 (memset) and the increment produces 1, identical to the old behaviour.  On subsequent hotplug cycles the generation advances beyond any value a vCPU previously observed on this CPU, so the generation check in pre_svm_run() reliably forces new_asid() on every vCPU after every hotplug cycle.","modified":"2026-09-08T17:00:15.210269308Z","published":"2026-08-10T13:19:53.303Z","upstream":["CVE-2026-68093"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-68093"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.187-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.170-1","6.1.170-2","6.1.170-3","6.1.172-1","6.1.174-1","6.1.176-1","6.1.177-1","6.1.180-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not 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