{
  "cveId": "CVE-2026-99140",
  "url": "https://patchblox.com/security/cve/CVE-2026-99140",
  "summary": "CVE-2026-99140 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-99140, released November 3, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "tracing: Fix hist trigger timestamps for buffered events",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  tracing: Fix hist trigger timestamps for buffered events  Syzkaller triggered a WARN_ON_ONCE(!nest) warning:    WARNING: kernel/trace/ring_buffer.c:821 at ring_buffer_event_time_stamp   Call trace:     ring_buffer_event_time_stamp     hist_field_timestamp     hist_fn_call     event_hist_trigger     event_triggers_call     __event_trigger_test_discard     trace_event_buffer_commit     do_trace_event_raw_event_sched_switch     trace_event_raw_event_sched_switch  The warning is probabilistically reproducible and is related to syzkaller executing the following commands:    echo \u0027prev_pid == 999999\u0027 \u003E events/sched/sched_switch/filter   echo \u0027hist:keys=common_timestamp\u0027 \u003E events/sched/sched_switch/trigger  The specific triggering process is as follows:  CPU 0                                           CPU 1 (context switching)                             (echo \u0027hist:keys=common_timestamp\u0027 \u003E \\                                                         events/sched/sched_switch/trigger) do_trace_event_raw_event_##call   trace_event_buffer_lock_reserve     if (!tr-\u003Eno_filter_buffering_ref \u0026\u0026         trace_file-\u003Eflags \u0026 EVENT_FILE_FL_FILTERED)         return entry;  // return directly                                                 event_hist_trigger_parse                                                   hist_register_trigger                                                     tracing_set_filter_buffering(file-\u003Etr, true);                                                       tr-\u003Eno_filter_buffering_ref\u002B\u002B;     __trace_buffer_lock_reserve       rb_start_commit         local_inc(\u0026cpu_buffer-\u003Ecommitting);  // skipped and not executed   trace_event_buffer_commit     __event_trigger_test_discard       event_triggers_call         event_hist_trigger           hist_fn_call             hist_field_timestamp               ring_buffer_event_time_stamp                 nest = local_read(\u0026cpu_buffer-\u003Ecommitting);                 WARN_ON_ONCE(!nest)  // trigger warning  The root cause is that when an event file has a filter attached and the hist trigger has not yet been attached, trace_event_buffer_lock_reserve() writes the event into the per-CPU trace_buffered_event temp buffer instead of reserving it in the ring buffer, so cpu_buffer-\u003Ecommitting is not incremented. When the event is later processed at commit time by a hist trigger, hist_field_timestamp() -\u003E ring_buffer_event_time_stamp() sees a zero committing count, triggering WARN_ON_ONCE(!nest).  tracing_event_time_stamp() was added by commit d8279bfc5e959 (\u0022tracing: Add tracing_event_time_stamp() API\u0022) for exactly this case: if the event is the per-CPU trace_buffered_event, it returns the current ring buffer timestamp. But it never gained a caller. Use it in hist_field_timestamp(), so that a hist trigger that races onto a buffered event records the current time, which is only marginally later than when the event was recorded, instead of warning and recording a bogus timestamp.",
  "published": "2026-10-28T11:17:33Z",
  "severity": "Moderate",
  "cvss": 5.5,
  "epss": 0.00173,
  "epssPercentile": 0.06794,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-99140",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.115-2",
      "fix": "DEBIAN-CVE-2026-99140",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-99140",
      "released": "2026-11-03T18:58:21Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.2.13-1",
      "fix": "DEBIAN-CVE-2026-99140",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-99140",
      "released": "2026-11-03T18:58:21Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T13:06:02Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}