{"id":"CVE-2022-48943","state":"PUBLISHED","title":"KVM: x86/mmu: make apf token non-zero to fix bug","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86/mmu: make apf token non-zero to fix bug\n\nIn current async pagefault logic, when a page is ready, KVM relies on\nkvm_arch_can_dequeue_async_page_present() to determine whether to deliver\na READY event to the Guest. This function test token value of struct\nkvm_vcpu_pv_apf_data, which must be reset to zero by Guest kernel when a\nREADY event is finished by Guest. If value is zero meaning that a READY\nevent is done, so the KVM can deliver another.\nBut the kvm_arch_setup_async_pf() may produce a valid token with zero\nvalue, which is confused with previous mention and may lead the loss of\nthis READY event.\n\nThis bug may cause task blocked forever in Guest:\n INFO: task stress:7532 blocked for more than 1254 seconds.\n       Not tainted 5.10.0 #16\n \"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\" disables this message.\n task:stress          state:D stack:    0 pid: 7532 ppid:  1409\n flags:0x00000080\n Call Trace:\n  __schedule+0x1e7/0x650\n  schedule+0x46/0xb0\n  kvm_async_pf_task_wait_schedule+0xad/0xe0\n  ? exit_to_user_mode_prepare+0x60/0x70\n  __kvm_handle_async_pf+0x4f/0xb0\n  ? asm_exc_page_fault+0x8/0x30\n  exc_page_fault+0x6f/0x110\n  ? asm_exc_page_fault+0x8/0x30\n  asm_exc_page_fault+0x1e/0x30\n RIP: 0033:0x402d00\n RSP: 002b:00007ffd31912500 EFLAGS: 00010206\n RAX: 0000000000071000 RBX: ffffffffffffffff RCX: 00000000021a32b0\n RDX: 000000000007d011 RSI: 000000000007d000 RDI: 00000000021262b0\n RBP: 00000000021262b0 R08: 0000000000000003 R09: 0000000000000086\n R10: 00000000000000eb R11: 00007fefbdf2baa0 R12: 0000000000000000\n R13: 0000000000000002 R14: 000000000007d000 R15: 0000000000001000","publishedAt":"2024-08-22T03:30:14.027Z","updatedAt":"2026-08-05T08:53:03.401Z","severity":{"score":7.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"2635b5c4a0e407b84f68e188c719f28ba0e9ae1b","status":"affected","lessThan":"72fdfc75d4217b32363cc80def3de2cb3fef3f02","versionType":"git"},{"version":"2635b5c4a0e407b84f68e188c719f28ba0e9ae1b","status":"affected","lessThan":"4c3644b6c96c5daa5149e5abddc07234eea47c7c","versionType":"git"},{"version":"2635b5c4a0e407b84f68e188c719f28ba0e9ae1b","status":"affected","lessThan":"62040f5cd7d937de547836e747b6aa8212fec573","versionType":"git"},{"version":"2635b5c4a0e407b84f68e188c719f28ba0e9ae1b","status":"affected","lessThan":"6f3c1fc53d86d580d8d6d749c4af23705e4f6f79","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/mmu/mmu.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.8","versionType":"semver"},{"version":"5.10.103","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.26","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"5.16.12","status":"unaffected","lessThanOrEqual":"5.16.*","versionType":"semver"},{"version":"5.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/mmu/mmu.c"]}],"references":["https://git.kernel.org/stable/c/72fdfc75d4217b32363cc80def3de2cb3fef3f02","https://git.kernel.org/stable/c/4c3644b6c96c5daa5149e5abddc07234eea47c7c","https://git.kernel.org/stable/c/62040f5cd7d937de547836e747b6aa8212fec573","https://git.kernel.org/stable/c/6f3c1fc53d86d580d8d6d749c4af23705e4f6f79"],"weaknesses":[],"ingestedAt":"2026-10-29T20:05:26.763Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2022/48xxx/CVE-2022-48943.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2022-48943","state":"PUBLISHED","datePublished":"2024-08-22T03:30:14.027Z","dateUpdated":"2026-08-05T08:53:03.401Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-08-22T01:27:53.623Z"},"containers":{"cna":{"title":"KVM: x86/mmu: make apf token non-zero to fix bug","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86/mmu: make apf token non-zero to fix bug\n\nIn current async pagefault logic, when a page is ready, KVM relies on\nkvm_arch_can_dequeue_async_page_present() to determine whether to deliver\na READY event to the Guest. This function test token value of struct\nkvm_vcpu_pv_apf_data, which must be reset to zero by Guest kernel when a\nREADY event is finished by Guest. If value is zero meaning that a READY\nevent is done, so the KVM can deliver another.\nBut the kvm_arch_setup_async_pf() may produce a valid token with zero\nvalue, which is confused with previous mention and may lead the loss of\nthis READY event.\n\nThis bug may cause task blocked forever in Guest:\n INFO: task stress:7532 blocked for more than 1254 seconds.\n       Not tainted 5.10.0 #16\n \"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\" disables this message.\n task:stress          state:D stack:    0 pid: 7532 ppid:  1409\n flags:0x00000080\n Call Trace:\n  __schedule+0x1e7/0x650\n  schedule+0x46/0xb0\n  kvm_async_pf_task_wait_schedule+0xad/0xe0\n  ? exit_to_user_mode_prepare+0x60/0x70\n  __kvm_handle_async_pf+0x4f/0xb0\n  ? asm_exc_page_fault+0x8/0x30\n  exc_page_fault+0x6f/0x110\n  ? asm_exc_page_fault+0x8/0x30\n  asm_exc_page_fault+0x1e/0x30\n RIP: 0033:0x402d00\n RSP: 002b:00007ffd31912500 EFLAGS: 00010206\n RAX: 0000000000071000 RBX: ffffffffffffffff RCX: 00000000021a32b0\n RDX: 000000000007d011 RSI: 000000000007d000 RDI: 00000000021262b0\n RBP: 00000000021262b0 R08: 0000000000000003 R09: 0000000000000086\n R10: 00000000000000eb R11: 00007fefbdf2baa0 R12: 0000000000000000\n R13: 0000000000000002 R14: 000000000007d000 R15: 0000000000001000"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"2635b5c4a0e407b84f68e188c719f28ba0e9ae1b","status":"affected","lessThan":"72fdfc75d4217b32363cc80def3de2cb3fef3f02","versionType":"git"},{"version":"2635b5c4a0e407b84f68e188c719f28ba0e9ae1b","status":"affected","lessThan":"4c3644b6c96c5daa5149e5abddc07234eea47c7c","versionType":"git"},{"version":"2635b5c4a0e407b84f68e188c719f28ba0e9ae1b","status":"affected","lessThan":"62040f5cd7d937de547836e747b6aa8212fec573","versionType":"git"},{"version":"2635b5c4a0e407b84f68e188c719f28ba0e9ae1b","status":"affected","lessThan":"6f3c1fc53d86d580d8d6d749c4af23705e4f6f79","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/mmu/mmu.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.8","versionType":"semver"},{"version":"5.10.103","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.26","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"5.16.12","status":"unaffected","lessThanOrEqual":"5.16.*","versionType":"semver"},{"version":"5.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/mmu/mmu.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/72fdfc75d4217b32363cc80def3de2cb3fef3f02"},{"url":"https://git.kernel.org/stable/c/4c3644b6c96c5daa5149e5abddc07234eea47c7c"},{"url":"https://git.kernel.org/stable/c/62040f5cd7d937de547836e747b6aa8212fec573"},{"url":"https://git.kernel.org/stable/c/6f3c1fc53d86d580d8d6d749c4af23705e4f6f79"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","baseScore":7.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is reached only when a KVM guest takes a paravirtual async page fault (KVM_RUN → faultin → kvm_arch_setup_async_pf), which requires local code execution inside a VM or local /dev/kvm use—not remote packet processing.\nAC:L - On overcommitted KVM hosts (common cloud deployments) async PF is routinely exercised; token 0 is produced deterministically on vCPU 0 when (id<<12)==0, and concurrent READY completions that drop that event are driven by attacker/workload-controlled multi-threaded memory stress, as in the original hang report.\nPR:N - No host privileges are required—an ordinary tenant VM triggers this via normal guest userspace page faults after the guest kernel enables MSR_KVM_ASYNC_PF_EN, matching other guest-triggerable KVM DoS scores (PR:N relative to the host).\nUI:N - No separate victim action is needed; guest memory accesses under host reclaim/async PF delivery alone hit the vulnerable token path.\nS:C - The vulnerable code is host KVM MMU/async-PF handling, but the impact is permanent denial of guest task/VM progress across the hypervisor–guest (and nested L1/L2) security boundary, consistent with other host-KVM guest-availability DoS scorings.\nC:N - This is solely a confused zero token versus the READY-slot-empty sentinel causing a lost wakeup; there is no OOB read, UAF, or other disclosure primitive.\nI:N - No memory corruption, write primitive, or control-flow hijack occurs—only failure to deliver a READY notification for a valid token value of zero.\nA:H - A lost READY leaves the guest task blocked forever in TASK_UNINTERRUPTIBLE (D state), which is a complete denial of that workload’s availability and can stall nested guests depending on the hung threads."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T08:53:03.401Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"5.10.103"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"5.15.26"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"5.16.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"5.17"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2022-48943","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2024-09-10T15:33:08.943998Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-09-12T17:33:10.679Z"}}]}}}