CVE-2026-43363: Linux kernel · x86/apic: Disable x2apic on resume if the kernel expects so
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · patch available : update Linux kernel when convenient.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 8 May 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.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde@7.0.0-1008.8?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 25.10linuxpkg:deb/ubuntu/linux@6.17.0-40.40?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws@6.17.0-1019.19?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure@6.17.0-1020.20?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp@6.17.0-1020.22?arch=source&distro=questingOther threats | Affected
| 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 patch is available and should be applied to affected Linux kernel versions. The fix disables x2apic mode on resume if the kernel expects it to be disabled, preventing system hangs. Users should update their Linux kernel to a fixed version as provided by their distribution's security advisory, such as Ubuntu Security Notice USN-8567-1. No additional mitigation is required beyond applying the official fix.
Description
A vulnerability in the Linux kernel's x86 APIC handling was resolved by disabling x2apic mode on resume if the kernel expects it to be disabled. The issue occurs because firmware may re-enable x2apic mode after resuming from S2RAM sleep states, causing a mismatch between kernel expectations and hardware state that can lead to system hangs. The fix ensures that the kernel disables x2apic on resume when required, aligning with ACPI v6.6 specifications. This vulnerability affects specific Linux kernel versions and has a medium severity rating with a CVSS score of 5.5.
References
- ubuntu.com/security/CVE-2026-43363 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-43363 (opens in a new tab)
- git.kernel.org/linus/8cc7dd77a1466f0ec58c03478b2e735a5b289b96 (opens in a new tab)
- git.kernel.org/stable/c/11712c4eb384098db4cb08792e223c818b908c1a (opens in a new tab)
- git.kernel.org/stable/c/1a85f84214f9d790216547ac6086bf8033cd9e5a (opens in a new tab)
- git.kernel.org/stable/c/1d8440c1e7c49715f937416ac90cf260f1f1712c (opens in a new tab)
- git.kernel.org/stable/c/3dd0812a7c764cd8f3b0182441ac22da0a7f3b09 (opens in a new tab)
- git.kernel.org/stable/c/8cc7dd77a1466f0ec58c03478b2e735a5b289b96 (opens in a new tab)
- git.kernel.org/stable/c/965289b120cc68cca886c75219c68b8c15751d73 (opens in a new tab)
- git.kernel.org/stable/c/a6ad6f2e31b524cbb66b2f370bad0cf17d327e6c (opens in a new tab)
- git.kernel.org/stable/c/f591938072115bf08730b8530c67fab189cc6308 (opens in a new tab)
- ubuntu.com/security/notices/USN-8567-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8575-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8576-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8596-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8575-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8576-2 (opens in a new tab)