CVE-2026-43265: Linux kernel · KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in ec3be7dc9391085a2d96700e159d66d1328b7ff6 : update Linux kernel when convenient.
Data as of 6 Nov 2026, 15:49 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-11-06.
- Patch
- Available – fixed in ec3be7dc9391085a2d96700e159d66d1328b7ff6, ead63640d4e72e6f6d464f4e31f7fecb79af8869, 2657439265d34a911886b916ba8be97ecc117d51 +3
Exploitation evidence
Disclosed: evidence found.
CVE published 6 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 6 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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Description
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.
References
- git.kernel.org/stable/c/78265cd066d73a5cb41c088fcae4a2515e480d97 (opens in a new tab)
- git.kernel.org/stable/c/ec3be7dc9391085a2d96700e159d66d1328b7ff6 (opens in a new tab)
- git.kernel.org/stable/c/2657439265d34a911886b916ba8be97ecc117d51 (opens in a new tab)
- git.kernel.org/stable/c/1e88b5f854bdb469424132e0bb44793ad7a7c20a (opens in a new tab)
- git.kernel.org/stable/c/1c957773063ed3264953597e32990a748381caf6 (opens in a new tab)
- git.kernel.org/stable/c/ead63640d4e72e6f6d464f4e31f7fecb79af8869 (opens in a new tab)