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

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于恢复时x2apic模式未按预期禁用，可能导致系统挂起。

AI Predicted 7.5 Difficulty: Moderate EPSS 0.12% · P2

Possible ATT&CK Techniques 1 AI

T1620 · Reflective Code Loading

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 6e1cb38a2aef7680975e71f23de187859ee8b158< a6ad6f2e31b524cbb66b2f370bad0cf17d327e6c affected
6e1cb38a2aef7680975e71f23de187859ee8b158< 3dd0812a7c764cd8f3b0182441ac22da0a7f3b09 affected
6e1cb38a2aef7680975e71f23de187859ee8b158< 965289b120cc68cca886c75219c68b8c15751d73 affected
6e1cb38a2aef7680975e71f23de187859ee8b158< f591938072115bf08730b8530c67fab189cc6308 affected
6e1cb38a2aef7680975e71f23de187859ee8b158< 1a85f84214f9d790216547ac6086bf8033cd9e5a affected
6e1cb38a2aef7680975e71f23de187859ee8b158< 11712c4eb384098db4cb08792e223c818b908c1a affected
6e1cb38a2aef7680975e71f23de187859ee8b158< 1d8440c1e7c49715f937416ac90cf260f1f1712c affected
6e1cb38a2aef7680975e71f23de187859ee8b158< 8cc7dd77a1466f0ec58c03478b2e735a5b289b96 affected
… +10 more rows
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I. Basic Information for CVE-2026-43363

Vulnerability Information
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Vulnerability Title
x86/apic: Disable x2apic on resume if the kernel expects so
Source: CVE Program / CVE List V5
Vulnerability 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. ]
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于恢复时x2apic模式未按预期禁用，可能导致系统挂起。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 6e1cb38a2aef7680975e71f23de187859ee8b158 ~ a6ad6f2e31b524cbb66b2f370bad0cf17d327e6c -
Linux Linux 2.6.28 -

II. Public POCs for CVE-2026-43363

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III. Intelligence Information for CVE-2026-43363

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Patches & Fixes for CVE-2026-43363 (8)

Same Patch Batch · Linux · 2026-05-08 · 197 CVEs total

CVE-2026-43341 9.8 CRITICAL net/ipv6: ioam6: prevent schema length wraparound in trace fill
CVE-2026-43402 9.8 CRITICAL kthread: consolidate kthread exit paths to prevent use-after-free
CVE-2026-43414 9.8 CRITICAL scsi: qla2xxx: Completely fix fcport double free
CVE-2026-43384 9.8 CRITICAL net/tcp-ao: Fix MAC comparison to be constant-time
CVE-2026-43304 9.8 CRITICAL libceph: define and enforce CEPH_MAX_KEY_LEN
CVE-2026-43379 9.8 CRITICAL ksmbd: fix use-after-free in smb_lazy_parent_lease_break_close()
CVE-2026-43376 9.8 CRITICAL ksmbd: fix use-after-free by using call_rcu() for oplock_info
CVE-2026-43465 9.8 CRITICAL net/mlx5e: RX, Fix XDP multi-buf frag counting for striding RQ
CVE-2026-43378 9.8 CRITICAL smb: server: fix use-after-free in smb2_open()
CVE-2026-43383 9.4 CRITICAL net/tcp-md5: Fix MAC comparison to be constant-time
CVE-2026-43406 9.1 CRITICAL libceph: prevent potential out-of-bounds reads in process_message_header()
CVE-2026-43407 9.1 CRITICAL libceph: Fix potential out-of-bounds access in ceph_handle_auth_reply()
CVE-2026-43284 8.8 HIGH xfrm: esp: avoid in-place decrypt on shared skb frags
CVE-2026-43334 8.8 HIGH Bluetooth: SMP: force responder MITM requirements before building the pairing response
CVE-2026-43322 8.8 HIGH Bluetooth: hci_sync: Fix UAF in le_read_features_complete
CVE-2026-43403 8.8 HIGH nsfs: tighten permission checks for ns iteration ioctls
CVE-2026-43391 8.8 HIGH nsfs: tighten permission checks for handle opening
CVE-2026-43291 8.3 HIGH net: nfc: nci: Fix parameter validation for packet data
CVE-2026-43365 8.2 HIGH xfs: fix undersized l_iclog_roundoff values
CVE-2026-43466 8.2 HIGH net/mlx5e: Fix DMA FIFO desync on error CQE SQ recovery

Showing top 20 of 197 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-43363

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