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CVE Record

CVE-2024-35995: ACPI: CPPC: Use access_width over bit_width for system memory accesses

In the Linux kernel, the following vulnerability has been resolved: ACPI: CPPC: Use access_width over bit_width for system memory accesses To align with ACPI 6.3+, since bit_width can be any 8-bit value, it cannot be depended on to be always on a clean 8b boundary. This was uncovered on the Cobalt 100 platform. SError Interrupt on CPU26, code 0xbe000011 -- SError CPU: 26 PID: 1510 Comm: systemd-udevd Not tainted 5.15.2.1-13 #1 Hardware name: MICROSOFT CORPORATION, BIOS MICROSOFT CORPORATION pstate: 62400009 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) pc : cppc_get_perf_caps+0xec/0x410 lr : cppc_get_perf_caps+0xe8/0x410 sp : ffff8000155ab730 x29: ffff8000155ab730 x28: ffff0080139d0038 x27: ffff0080139d0078 x26: 0000000000000000 x25: ffff0080139d0058 x24: 00000000ffffffff x23: ffff0080139d0298 x22: ffff0080139d0278 x21: 0000000000000000 x20: ffff00802b251910 x19: ffff0080139d0000 x18: ffffffffffffffff x17: 0000000000000000 x16: ffffdc7e111bad04 x15: ffff00802b251008 x14: ffffffffffffffff x13: ffff013f1fd63300 x12: 0000000000000006 x11: ffffdc7e128f4420 x10: 0000000000000000 x9 : ffffdc7e111badec x8 : ffff00802b251980 x7 : 0000000000000000 x6 : ffff0080139d0028 x5 : 0000000000000000 x4 : ffff0080139d0018 x3 : 00000000ffffffff x2 : 0000000000000008 x1 : ffff8000155ab7a0 x0 : 0000000000000000 Kernel panic - not syncing: Asynchronous SError Interrupt CPU: 26 PID: 1510 Comm: systemd-udevd Not tainted 5.15.2.1-13 #1 Hardware name: MICROSOFT CORPORATION, BIOS MICROSOFT CORPORATION Call trace: dump_backtrace+0x0/0x1e0 show_stack+0x24/0x30 dump_stack_lvl+0x8c/0xb8 dump_stack+0x18/0x34 panic+0x16c/0x384 add_taint+0x0/0xc0 arm64_serror_panic+0x7c/0x90 arm64_is_fatal_ras_serror+0x34/0xa4 do_serror+0x50/0x6c el1h_64_error_handler+0x40/0x74 el1h_64_error+0x7c/0x80 cppc_get_perf_caps+0xec/0x410 cppc_cpufreq_cpu_init+0x74/0x400 [cppc_cpufreq] cpufreq_online+0x2dc/0xa30 cpufreq_add_dev+0xc0/0xd4 subsys_interface_register+0x134/0x14c cpufreq_register_driver+0x1b0/0x354 cppc_cpufreq_init+0x1a8/0x1000 [cppc_cpufreq] do_one_initcall+0x50/0x250 do_init_module+0x60/0x27c load_module+0x2300/0x2570 __do_sys_finit_module+0xa8/0x114 __arm64_sys_finit_module+0x2c/0x3c invoke_syscall+0x78/0x100 el0_svc_common.constprop.0+0x180/0x1a0 do_el0_svc+0x84/0xa0 el0_svc+0x2c/0xc0 el0t_64_sync_handler+0xa4/0x12c el0t_64_sync+0x1a4/0x1a8 Instead, use access_width to determine the size and use the offset and width to shift and mask the bits to read/write out. Make sure to add a check for system memory since pcc redefines the access_width to subspace id. If access_width is not set, then fall back to using bit_width. [ rjw: Subject and changelog edits, comment adjustments ]

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can cause a system crash on platforms where ACPI CPPC reports system-memory register widths in a way the kernel handled incorrectly. The public report shows a kernel panic on Microsoft Cobalt 100 hardware. The main business risk is availability disruption on affected Linux systems, not confirmed data theft or remote compromise.

Executive priority

Treat as a targeted availability risk for Linux infrastructure on affected hardware rather than an internet-wide emergency. Patch through normal kernel maintenance, escalating priority for production systems where a kernel panic would cause service outage or where Cobalt 100-class platforms are deployed.

Technical view

The ACPI CPPC code used bit_width to size system-memory accesses, but ACPI 6.3+ allows bit_width values that are not clean byte boundaries. The fix uses access_width for system-memory access sizing, then shifts and masks by offset and width, falling back to bit_width when access_width is unset.

Likely exposure

Exposure appears limited to Linux systems using ACPI CPPC paths on affected kernel versions and platform firmware combinations, with Cobalt 100 explicitly mentioned. The CVE data lists Linux as affected and provides stable kernel fixes, but does not define a broad remotely reachable attack surface.

Exploitation context

The bundle reports no KEV listing and provides no evidence of active exploitation. The described failure occurred during cppc_cpufreq initialization and produced an arm64 SError kernel panic. Sources do not show a public exploit, attacker requirements, or remote trigger path.

Researcher notes

Evidence is strongest for an ACPI CPPC system-memory access-width bug causing panic on a specific platform. The source bundle does not include CVSS, CWE, exploitability details, or distribution package mapping. Avoid assuming remote exploitability; focus validation on kernel line, ACPI CPPC usage, and fixed commit presence.

Mitigation direction

  • Apply vendor or distribution kernel updates containing the referenced stable fixes.
  • Prioritize affected arm64 platforms using ACPI CPPC, especially Cobalt 100-like hardware.
  • Check Linux distribution advisories for exact package versions and reboot requirements.
  • If patching is delayed, monitor for kernel panics in cppc_get_perf_caps or cppc_cpufreq paths.

Validation and detection

  • Inventory running kernel versions across Linux hosts and appliances.
  • Map affected systems to hardware platforms using ACPI CPPC or cppc_cpufreq.
  • Confirm distribution packages include the upstream stable commits or later fixes.
  • Review crash logs for SError, cppc_get_perf_caps, or cppc_cpufreq initialization failures.
Prepared
Confidence
medium
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
8Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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ADP provider summaries

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other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux5bbb86aa4b8d84395e42cd05448820651d79f349, 5bbb86aa4b8d84395e42cd05448820651d79f349, 5bbb86aa4b8d84395e42cd05448820651d79f349, 5bbb86aa4b8d84395e42cd05448820651d79f349unaffected
LinuxLinux4.9, 0, 6.1.90, 6.6.30, 6.8.9, 6.9affected
Weakness

CWE details

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