CVE-2026-99178

Что произошло

In the Linux kernel, the following vulnerability has been resolved: x86/kvm: Don't consume async #PF flags on a kernel #PF in NMI context An async #PF "page not present" event arrives through the #PF vector, and its reason sits in the per-CPU apf_reason.flags until __kvm_handle_async_pf() reads and clears it. If an NMI arrives after the event is injected and before the #PF handler reads the flags, and the NMI handler itself takes a #PF, that fault reads and clears the flags belonging to the #PF it interrupted. It then finds interrupts disabled in the NMI context it interrupted, and panics: Kernel panic - not syncing: Host injected async #PF in interrupt disabled region Call Trace: panic+0x52/0x60 __kvm_handle_async_pf+0xb0/0xb0 exc_page_fault+0x71/0xb0 asm_exc_page_fault+0x27/0x30 RIP: 0010:__get_user_nocheck_8+0x6/0x20 perf_callchain_user+0x147/0x1a0 get_perf_callchain+0x12d/0x1c0 ... perf_event_nmi_handler+0x26/0x50 exc_nmi+0xe8/0x110 RIP: 0010:asm_exc_page_fault+0x0/0x30 The last RIP line shows the NMI landing on the first instruction of the #PF entry. perf with user call chains takes such a fault: the sampling NMI walks the user stack with __get_user(), which faults when a saved frame pointer is not a valid user address or the walk runs off the top of the stack. The same window exists when KVM, running as an L1 hypervisor with DELIVERY_AS_PF_VMEXIT, reads the flags itself after a #PF VM-exit. The NMI entry code saves and restores CR2 for this nesting, but not the async #PF reason. Andy Lutomirski described the race, with perf as the example, when async #PF delivery was reworked in 2020 [1]. Saving and clearing the flags across the NMI, next to CR2, was discussed there but not merged. Since that rework, Linux has stopped setting KVM_ASYNC_PF_SEND_ALWAYS, so the host delivers "page not present" only for user mode faults and a kernel-mode fault in NMI context (including kernel-mode #MC and #DB) cannot be an async page fault. In that case, return without touching the flags so that the interrupted handler finds them intact. Tested on v7.3-rc5 in a 4-vCPU, 2 GiB guest restored from a snapshot whose memory is served on demand through userfaultfd, so that reading it back takes async #PFs, while every thread samples hardware cycles with user call chains and points its frame pointer at an unmapped page. Without this patch the guest panicked as above in 3 of 3 runs. With it, the guest survived 3 of 3 runs of 60 seconds, and the host counted 148,441 to 153,334 kvm_async_pf_not_present events in the first 20 seconds of each. On 6.18.50 the results were the same: the guest panicked without the patch and survived with it.

Что делать

dpkg-query -W -f='${Package}	${Version}\n'

rpm -qa --qf '%{NAME}\t%{VERSION}-%{RELEASE}\n'

Get-HotFix | Select-Object HotFixID, InstalledOn

Продукты и затронутые версии

{
  "status": "affected",
  "version": "631bc4878220932fe67fc46fc7cf7cccdb1ec597",
  "lessThan": "fd60b32a99627fda479c9fa1d4a82fa9f7994670",
  "versionType": "git"
}

{
  "status": "affected",
  "version": "631bc4878220932fe67fc46fc7cf7cccdb1ec597",
  "lessThan": "b77e9622bbade9812e2090c66d25c372f515e921",
  "versionType": "git"
}

{
  "status": "affected",
  "version": "631bc4878220932fe67fc46fc7cf7cccdb1ec597",
  "lessThan": "f45ee1ff6358a22d7e22a4c53cb3148ea97b10d9",
  "versionType": "git"
}

{
  "status": "affected",
  "version": "631bc4878220932fe67fc46fc7cf7cccdb1ec597",
  "lessThan": "81d99abe2bd81379abfb595e403bbbee6fbfc624",
  "versionType": "git"
}

{
  "status": "affected",
  "version": "2.6.38"
}

{
  "status": "unaffected",
  "version": "0",
  "lessThan": "2.6.38",
  "versionType": "semver"
}

{
  "status": "unaffected",
  "version": "6.12.115",
  "versionType": "semver",
  "lessThanOrEqual": "6.12.*"
}

{
  "status": "unaffected",
  "version": "6.18.59",
  "versionType": "semver",
  "lessThanOrEqual": "6.18.*"
}

{
  "status": "unaffected",
  "version": "7.2.13",
  "versionType": "semver",
  "lessThanOrEqual": "7.2.*"
}

{
  "status": "unaffected",
  "version": "7.3",
  "versionType": "original_commit_for_fix",
  "lessThanOrEqual": "*"
}

CVSS: оценки и векторы

Оценка CVSS отсутствует.

Источники и ссылки

{
  "cwes": [],
  "epss": {
    "source": "epss",
    "received_at": "2026-11-02T21:15:56.599720+00:00"
  },
  "title": {
    "source": "cve",
    "received_at": "2026-11-01T21:02:04.874076+00:00"
  },
  "scores": [],
  "status": {
    "source": "cve",
    "received_at": "2026-11-01T21:02:04.874076+00:00"
  },
  "affected": [
    "cve"
  ],
  "published": {
    "source": "cve",
    "received_at": "2026-11-01T21:02:04.874076+00:00"
  },
  "solutions": [],
  "percentile": {
    "source": "epss",
    "received_at": "2026-11-02T21:15:56.599720+00:00"
  },
  "references": [
    "cve",
    "ghsa",
    "nvd"
  ],
  "description": {
    "source": "cve",
    "received_at": "2026-11-01T21:02:04.874076+00:00"
  },
  "workarounds": [],
  "configurations": []
}

Хронология записи

1. Данные обновлены03.11.2026, 00:15
2. Данные обновлены02.11.2026, 00:13
3. Данные обновлены02.11.2026, 00:02
4. Данные обновлены31.10.2026, 12:00
5. Данные обновлены30.10.2026, 15:58
6. Данные обновлены28.10.2026, 23:51
7. Данные обновлены28.10.2026, 18:00
8. Опубликована28.10.2026, 15:17

Личная заметка и статус

Другие CVE того же продукта