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VulnerabilityPublished Updated

CVE-2026-99178: Linux kernel · x86/kvm: Don't consume async #PF flags on a kernel #PF in NMI context

Affects Linux kernelSource GCVE Database

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Authoritative record:CVE-2026-99178· High

Not known to be exploited.

Data as of 30 Oct 2026, 03:51 UTC

Severity
High

Rated by Threat Radar · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 28 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu 26.10linuxpkg:deb/ubuntu/linux?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-14.14 – 7.3.0-10.10
7 affected builds
Fixed in–
Ubuntu 26.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1004.4 – 7.3.0-1004.4
6 affected builds
Fixed in–
Ubuntu 26.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1004.4 – 7.3.0-1004.4
6 affected builds
Fixed in–
Ubuntu 26.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1004.4 – 7.3.0-1004.5
4 affected builds
Fixed in–
Ubuntu 26.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1003.3 – 7.3.0-1004.4
6 affected builds
Fixed in–
Ubuntu 26.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1003.3 – 7.3.0-1004.4
6 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix for this vulnerability is available and should be applied to affected Linux kernel versions. The patch prevents the kernel panic by preserving async #PF flags during kernel page faults in NMI context. Systems running affected kernel versions with KVM nested virtualization should upgrade to a patched kernel release to avoid host crashes. No additional mitigations are indicated beyond applying the official fix.

Description

CVE-2026-99178 is a Linux kernel vulnerability affecting the x86 KVM subsystem. It involves improper handling of asynchronous page fault (#PF) flags during nested machine check or debug exceptions (NMI context). This flaw can cause a kernel panic when an NMI handler takes a page fault and clears flags belonging to the interrupted handler, leading to a crash. The issue was observed in scenarios involving KVM running as an L1 hypervisor and perf sampling with user call chains. The patch prevents consuming async #PF flags in kernel #PF in NMI context, avoiding the panic.

References

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