{
  "cveId": "CVE-2025-40122",
  "url": "https://patchblox.com/security/cve/CVE-2025-40122",
  "summary": "CVE-2025-40122 is fixed in linux on 1 platform by DEBIAN-CVE-2025-40122 (version 6.17.6-1), released November 12, 2025. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  perf/x86/intel: Fix IA32_PMC_x_CFG_B MSRs access...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  perf/x86/intel: Fix IA32_PMC_x_CFG_B MSRs access error  When running perf_fuzzer on PTL, sometimes the below \u0022unchecked MSR  access error\u0022 is seen when accessing IA32_PMC_x_CFG_B MSRs.  [   55.611268] unchecked MSR access error: WRMSR to 0x1986 (tried to write 0x0000000200000001) at rIP: 0xffffffffac564b28 (native_write_msr\u002B0x8/0x30) [   55.611280] Call Trace: [   55.611282]  \u003CTASK\u003E [   55.611284]  ? intel_pmu_config_acr\u002B0x87/0x160 [   55.611289]  intel_pmu_enable_acr\u002B0x6d/0x80 [   55.611291]  intel_pmu_enable_event\u002B0xce/0x460 [   55.611293]  x86_pmu_start\u002B0x78/0xb0 [   55.611297]  x86_pmu_enable\u002B0x218/0x3a0 [   55.611300]  ? x86_pmu_enable\u002B0x121/0x3a0 [   55.611302]  perf_pmu_enable\u002B0x40/0x50 [   55.611307]  ctx_resched\u002B0x19d/0x220 [   55.611309]  __perf_install_in_context\u002B0x284/0x2f0 [   55.611311]  ? __pfx_remote_function\u002B0x10/0x10 [   55.611314]  remote_function\u002B0x52/0x70 [   55.611317]  ? __pfx_remote_function\u002B0x10/0x10 [   55.611319]  generic_exec_single\u002B0x84/0x150 [   55.611323]  smp_call_function_single\u002B0xc5/0x1a0 [   55.611326]  ? __pfx_remote_function\u002B0x10/0x10 [   55.611329]  perf_install_in_context\u002B0xd1/0x1e0 [   55.611331]  ? __pfx___perf_install_in_context\u002B0x10/0x10 [   55.611333]  __do_sys_perf_event_open\u002B0xa76/0x1040 [   55.611336]  __x64_sys_perf_event_open\u002B0x26/0x30 [   55.611337]  x64_sys_call\u002B0x1d8e/0x20c0 [   55.611339]  do_syscall_64\u002B0x4f/0x120 [   55.611343]  entry_SYSCALL_64_after_hwframe\u002B0x76/0x7e  On PTL, GP counter 0 and 1 doesn\u0027t support auto counter reload feature, thus it would trigger a #GP when trying to write 1 on bit 0 of CFG_B MSR which requires to enable auto counter reload on GP counter 0.  The root cause of causing this issue is the check for auto counter reload (ACR) counter mask from user space is incorrect in intel_pmu_acr_late_setup() helper. It leads to an invalid ACR counter mask from user space could be set into hw.config1 and then written into CFG_B MSRs and trigger the MSR access warning.  e.g., User may create a perf event with ACR counter mask (config2=0xcb), and there is only 1 event created, so \u0022cpuc-\u003En_events\u0022 is 1.  The correct check condition should be \u0022i \u002B idx \u003E= cpuc-\u003En_events\u0022 instead of \u0022i \u002B idx \u003E cpuc-\u003En_events\u0022 (it looks a typo). Otherwise, the counter mask would traverse twice and an invalid \u0022cpuc-\u003Eassign[1]\u0022 bit (bit 0) is set into hw.config1 and cause MSR accessing error.  Besides, also check if the ACR counter mask corresponding events are ACR events. If not, filter out these counter mask. If a event is not a ACR event, it could be scheduled to an HW counter which doesn\u0027t support ACR. It\u0027s invalid to add their counter index in ACR counter mask.  Furthermore, remove the WARN_ON_ONCE() since it\u0027s easily triggered as user could set any invalid ACR counter mask and the warning message could mislead users.",
  "published": "2025-11-12T11:15:41Z",
  "severity": "",
  "epss": 0.00198,
  "epssPercentile": 0.09651,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "6.17.6-1",
      "fix": "DEBIAN-CVE-2025-40122",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2025-40122",
      "released": "2025-11-12T11:15:41Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-09T01:18:40Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}