VulnerabilityPublished 28 Oct 2026

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

Source GCVE Database

Authoritative record:CVE-2026-99178

Not known to be exploited · fixed in f45ee1ff6358a22d7e22a4c53cb3148ea97b10d9 : patch Linux kernel soon.

Data as of 28 Oct 2026, 13:43 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Patch: Available – fixed in f45ee1ff6358a22d7e22a4c53cb3148ea97b10d9, b77e9622bbade9812e2090c66d25c372f515e921, 81d99abe2bd81379abfb595e403bbbee6fbfc624 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-9w29-5gpq-xmv3

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected <6.18.59 <7.2.13	Fixed in f45ee1ff6358a22d7e22a4c53cb3148ea97b10d9 b77e9622bbade9812e2090c66d25c372f515e921 81d99abe2bd81379abfb595e403bbbee6fbfc624 7.2.13 6.18.59
Debiandebian/linux`pkg:deb/debian/linux`Other threats	Affected <6.18.59 <7.2.13	Fixed in 6.18.59 7.2.13

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 has been implemented and tested in Linux kernel versions including 7.3-rc5 and 6.18.50. Users should apply the official kernel updates containing this patch to prevent host kernel panics related to async #PF handling in NMI context. No additional mitigation steps are required beyond applying the patch.

Description

A vulnerability in the Linux kernel's x86 KVM subsystem involves improper handling of asynchronous page fault (async #PF) flags during a kernel page fault in non-maskable interrupt (NMI) context. This race condition can cause a kernel panic when an NMI triggers a page fault that clears async #PF flags prematurely. The issue has been resolved by ensuring the async #PF flags are not consumed in this scenario, preventing the panic.

Impact

The vulnerability causes a kernel panic on the host system running KVM when an async page fault is mishandled during an NMI context page fault. This can lead to denial of service by crashing the host kernel and affecting virtual machine stability. The panic occurs specifically when the async #PF flags are cleared prematurely, disrupting normal fault handling.

Summary

The Linux kernel's x86 KVM subsystem had a vulnerability where async #PF flags could be consumed incorrectly during a kernel page fault in NMI context. Specifically, if an NMI arrives after an async #PF event is injected but before the page fault handler reads and clears the flags, and the NMI handler itself takes a page fault, it clears the flags belonging to the interrupted page fault. This leads to a kernel panic with the message 'Host injected async #PF in interrupt disabled region'. The root cause is that the NMI entry code saves and restores CR2 but not the async #PF reason flags. The fix prevents consuming async #PF flags on kernel page faults in NMI context, preserving the flags for the interrupted handler. This fix was tested successfully on kernel version 7.3-rc5 and 6.18.50, preventing guest panics under conditions that previously caused crashes.

References

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