Linux Kernel
CVE-2024-26768
HIGH
Severity by source
AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Crash triggered solely by hypervisor or hardware CPU-count configuration, not network input; PR:H for required admin control; no confidentiality or integrity impact beyond system availability.
Primary rating from Vendor (416baaa9-dc9f-4396-8d5f-8c081fb06d67).
CVSS VectorVendor: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Lifecycle Timeline
6DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
LoongArch: Change acpi_core_pic[NR_CPUS] to acpi_core_pic[MAX_CORE_PIC]
With default config, the value of NR_CPUS is 64. When HW platform has more then 64 cpus, system will crash on these platforms. MAX_CORE_PIC is the maximum cpu number in MADT table (max physical number) which can exceed the supported maximum cpu number (NR_CPUS, max logical number), but kernel should not crash. Kernel should boot cpus with NR_CPUS, let the remainder cpus stay in BIOS.
The potential crash reason is that the array acpi_core_pic[NR_CPUS] can be overflowed when parsing MADT table, and it is obvious that CORE_PIC should be corresponding to physical core rather than logical core, so it is better to define the array as acpi_core_pic[MAX_CORE_PIC].
With the patch, system can boot up 64 vcpus with qemu parameter -smp 128, otherwise system will crash with the following message.
[ 0.000000] CPU 0 Unable to handle kernel paging request at virtual address 0000420000004259, era 90000000037a5f0c, ra 90000000037a46ec [ 0.000000] Oops[#1]: [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 6.8.0-rc2+ #192 [ 0.000000] Hardware name: QEMU QEMU Virtual Machine, BIOS unknown 2/2/2022 [ 0.000000] pc 90000000037a5f0c ra 90000000037a46ec tp 9000000003c90000 sp 9000000003c93d60 [ 0.000000] a0 0000000000000019 a1 9000000003d93bc0 a2 0000000000000000 a3 9000000003c93bd8 [ 0.000000] a4 9000000003c93a74 a5 9000000083c93a67 a6 9000000003c938f0 a7 0000000000000005 [ 0.000000] t0 0000420000004201 t1 0000000000000000 t2 0000000000000001 t3 0000000000000001 [ 0.000000] t4 0000000000000003 t5 0000000000000000 t6 0000000000000030 t7 0000000000000063 [ 0.000000] t8 0000000000000014 u0 ffffffffffffffff s9 0000000000000000 s0 9000000003caee98 [ 0.000000] s1 90000000041b0480 s2 9000000003c93da0 s3 9000000003c93d98 s4 9000000003c93d90 [ 0.000000] s5 9000000003caa000 s6 000000000a7fd000 s7 000000000f556b60 s8 000000000e0a4330 [ 0.000000] ra: 90000000037a46ec platform_init+0x214/0x250 [ 0.000000] ERA: 90000000037a5f0c efi_runtime_init+0x30/0x94 [ 0.000000] CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) [ 0.000000] PRMD: 00000000 (PPLV0 -PIE -PWE) [ 0.000000] EUEN: 00000000 (-FPE -SXE -ASXE -BTE) [ 0.000000] ECFG: 00070800 (LIE=11 VS=7) [ 0.000000] ESTAT: 00010000 [PIL] (IS= ECode=1 EsubCode=0) [ 0.000000] BADV: 0000420000004259 [ 0.000000] PRID: 0014c010 (Loongson-64bit, Loongson-3A5000) [ 0.000000] Modules linked in: [ 0.000000] Process swapper (pid: 0, threadinfo=(____ptrval____), task=(____ptrval____)) [ 0.000000] Stack : 9000000003c93a14 9000000003800898 90000000041844f8 90000000037a46ec [ 0.000000] 000000000a7fd000 0000000008290000 0000000000000000 0000000000000000 [ 0.000000] 0000000000000000 0000000000000000 00000000019d8000 000000000f556b60 [ 0.000000] 000000000a7fd000 000000000f556b08 9000000003ca7700 9000000003800000 [ 0.000000] 9000000003c93e50 9000000003800898 9000000003800108 90000000037a484c [ 0.000000] 000000000e0a4330 000000000f556b60 000000000a7fd000 000000000f556b08 [ 0.000000] 9000000003ca7700 9000000004184000 0000000000200000 000000000e02b018 [ 0.000000] 000000000a7fd000 90000000037a0790 9000000003800108 0000000000000000 [ 0.000000] 0000000000000000 000000000e0a4330 000000000f556b60 000000000a7fd000 [ 0.000000] 000000000f556b08 000000000eaae298 000000000eaa5040 0000000000200000 [ 0.000000] ... [ 0.000000] Call Trace: [ 0.000000] [<90000000037a5f0c>] efi_runtime_init+0x30/0x94 [ 0.000000] [<90000000037a46ec>] platform_init+0x214/0x250 [ 0.000000] [<90000000037a484c>] setup_arch+0x124/0x45c [ 0.000000] [<90000000037a0790>] start_kernel+0x90/0x670 [ 0.000000] [<900000000378b0d8>] kernel_entry+0xd8/0xdc
AnalysisAI
Boot-time buffer overflow in the LoongArch ACPI initialization path of the Linux kernel causes a deterministic kernel crash when the physical or virtual CPU count exceeds 64 (the default NR_CPUS limit). The statically-sized acpi_core_pic[NR_CPUS] array is overwritten during MADT table parsing whenever MAX_CORE_PIC exceeds NR_CPUS, corrupting adjacent kernel memory and producing an unrecoverable paging fault before userspace is reached. No active exploitation is confirmed (not in CISA KEV), and EPSS stands at 0.24% (14th percentile), consistent with the niche architecture and the specialized triggering conditions required.
Technical ContextAI
The flaw resides in the LoongArch architecture-specific ACPI CPU enumeration code (CWE-120: Classic Buffer Overflow). During early boot, platform_init() parses the ACPI MADT (Multiple APIC Description Table) to discover physical processor cores and populates the acpi_core_pic[] array. That array is statically allocated to NR_CPUS entries - 64 in a default kernel build - which represents the maximum number of logical, schedulable CPUs. However, the physical core count advertised in MADT (MAX_CORE_PIC) can legally exceed NR_CPUS on machines or VMs with large CPU counts, causing an out-of-bounds write into adjacent kernel data structures. The fix resizes the array to MAX_CORE_PIC so that MADT parsing can safely enumerate all physical entries and leave excess cores in BIOS without corrupting memory. Affected CPEs per NVD include cpe:2.3:o:linux:linux_kernel covering the 6.8-rc1, 6.8-rc2, and 6.8-rc3 pre-release series as well as prior stable branches before the fix commits were backported.
RemediationAI
The primary remediation is to apply the upstream kernel fix commits available at https://git.kernel.org/stable/c/0f6810e39898af2d2cabd9313e4dbc945fb5dfdd, https://git.kernel.org/stable/c/4551b30525cf3d2f026b92401ffe241eb04dfebe, and https://git.kernel.org/stable/c/88e189bd16e5889e44a41b3309558ebab78b9280 and upgrade to a patched stable kernel release that includes them. For LoongArch systems that cannot be immediately patched, a direct workaround is to restrict the virtual or physical CPU count to 64 or fewer: in QEMU this means setting -smp to 64 or below, which prevents the overflow without requiring a kernel rebuild. A second workaround - rebuilding the kernel with a higher NR_CPUS value - expands the logical CPU limit but does not fix the underlying design flaw (physical vs. logical array sizing) and may increase kernel memory usage. Physical LoongArch servers with more than 64 cores that cannot be patched should be considered non-functional at boot until the patch is applied, as the crash is deterministic and occurs before userspace initialization.
Same weakness CWE-120 – Classic Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
Leaving vuln.today