VulnerabilityPublished 8 May 2026Updated 6 Nov 2026

CVE-2026-43363: Linux kernel · x86/apic: Disable x2apic on resume if the kernel expects so

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in f591938072115bf08730b8530c67fab189cc6308 : update Linux kernel when convenient.

Data as of 6 Nov 2026, 15:49 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

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 f591938072115bf08730b8530c67fab189cc6308, a6ad6f2e31b524cbb66b2f370bad0cf17d327e6c, 965289b120cc68cca886c75219c68b8c15751d73 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 8 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.

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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 6e1cb38a2aef7680975e71f23de187859ee8b158, < f591938072115bf08730b8530c67fab189cc6308	Fixed in f591938072115bf08730b8530c67fab189cc6308
LinuxLinux	Affected ≥ 6e1cb38a2aef7680975e71f23de187859ee8b158, < a6ad6f2e31b524cbb66b2f370bad0cf17d327e6c	Fixed in a6ad6f2e31b524cbb66b2f370bad0cf17d327e6c
LinuxLinux	Affected ≥ 6e1cb38a2aef7680975e71f23de187859ee8b158, < 965289b120cc68cca886c75219c68b8c15751d73	Fixed in 965289b120cc68cca886c75219c68b8c15751d73
LinuxLinux	Affected ≥ 6e1cb38a2aef7680975e71f23de187859ee8b158, < 11712c4eb384098db4cb08792e223c818b908c1a	Fixed in 11712c4eb384098db4cb08792e223c818b908c1a
LinuxLinux	Affected ≥ 6e1cb38a2aef7680975e71f23de187859ee8b158, < 8cc7dd77a1466f0ec58c03478b2e735a5b289b96	Fixed in 8cc7dd77a1466f0ec58c03478b2e735a5b289b96
LinuxLinux	Affected ≥ 6e1cb38a2aef7680975e71f23de187859ee8b158, < 3dd0812a7c764cd8f3b0182441ac22da0a7f3b09	Fixed in 3dd0812a7c764cd8f3b0182441ac22da0a7f3b09

Description

In the Linux kernel, the following vulnerability has been resolved: x86/apic: Disable x2apic on resume if the kernel expects so When resuming from s2ram, firmware may re-enable x2apic mode, which may have been disabled by the kernel during boot either because it doesn't support IRQ remapping or for other reasons. This causes the kernel to continue using the xapic interface, while the hardware is in x2apic mode, which causes hangs. This happens on defconfig + bare metal + s2ram. Fix this in lapic_resume() by disabling x2apic if the kernel expects it to be disabled, i.e. when x2apic_mode = 0. The ACPI v6.6 spec, Section 16.3 [1] says firmware restores either the pre-sleep configuration or initial boot configuration for each CPU, including MSR state: When executing from the power-on reset vector as a result of waking from an S2 or S3 sleep state, the platform firmware performs only the hardware initialization required to restore the system to either the state the platform was in prior to the initial operating system boot, or to the pre-sleep configuration state. In multiprocessor systems, non-boot processors should be placed in the same state as prior to the initial operating system boot. (further ahead) If this is an S2 or S3 wake, then the platform runtime firmware restores minimum context of the system before jumping to the waking vector. This includes: CPU configuration. Platform runtime firmware restores the pre-sleep configuration or initial boot configuration of each CPU (MSR, MTRR, firmware update, SMBase, and so on). Interrupts must be disabled (for IA-32 processors, disabled by CLI instruction). (and other things) So at least as per the spec, re-enablement of x2apic by the firmware is allowed if "x2apic on" is a part of the initial boot configuration. [1] https://uefi.org/specs/ACPI/6.6/16_Waking_and_Sleeping.html#initialization [ bp: Massage. ]

References

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