CVE-2026-43265 (GCVE-0-2026-43265)
Vulnerability from cvelistv5 – Published: 2026-05-06 11:28 – Updated: 2026-05-06 11:28
VLAI?
Title
KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()
Summary
In the Linux kernel, the following vulnerability has been resolved:
KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()
Ignore -EBUSY when checking nested events after exiting a blocking state
while L2 is active, as exiting to userspace will generate a spurious
userspace exit, usually with KVM_EXIT_UNKNOWN, and likely lead to the VM's
demise. Continuing with the wakeup isn't perfect either, as *something*
has gone sideways if a vCPU is awakened in L2 with an injected event (or
worse, a nested run pending), but continuing on gives the VM a decent
chance of surviving without any major side effects.
As explained in the Fixes commits, it _should_ be impossible for a vCPU to
be put into a blocking state with an already-injected event (exception,
IRQ, or NMI). Unfortunately, userspace can stuff MP_STATE and/or injected
events, and thus put the vCPU into what should be an impossible state.
Don't bother trying to preserve the WARN, e.g. with an anti-syzkaller
Kconfig, as WARNs can (hopefully) be added in paths where _KVM_ would be
violating x86 architecture, e.g. by WARNing if KVM attempts to inject an
exception or interrupt while the vCPU isn't running.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux |
Affected:
26844fee6adee9b1557d2279b0506285de9ee82b , < 78265cd066d73a5cb41c088fcae4a2515e480d97
(git)
Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < ec3be7dc9391085a2d96700e159d66d1328b7ff6 (git) Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < 2657439265d34a911886b916ba8be97ecc117d51 (git) Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < 1e88b5f854bdb469424132e0bb44793ad7a7c20a (git) Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < 1c957773063ed3264953597e32990a748381caf6 (git) Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < ead63640d4e72e6f6d464f4e31f7fecb79af8869 (git) |
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"url": "https://git.kernel.org/stable/c/1c957773063ed3264953597e32990a748381caf6"
},
{
"url": "https://git.kernel.org/stable/c/ead63640d4e72e6f6d464f4e31f7fecb79af8869"
}
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"title": "KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()",
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"date": "2026-05-09",
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}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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