CVE-2026-89746 (GCVE-0-2026-89746)
Vulnerability from cvelistv5
Published
2026-09-11 19:46
Modified
2026-10-19 08:52
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: tracing: Fix use-after-free with same-name named triggers When two hist triggers on different events are registered with the same name=, the second one reuses the first as named_data. Both are added to tr->hist_vars by save_hist_vars() during event_hist_trigger_parse(), because save_hist_vars() is called before event_trigger_register() while the named reuse is only detected later, in hist_register_trigger(). In the named-data branch hist_register_trigger() then frees the second histogram's hist_data via destroy_hist_data(), but never removes its tr->hist_vars list entry, leaving a dangling pointer and leaking the trace_array reference it holds. A later hist trigger that references a variable makes find_var_file() walk tr->hist_vars and dereference the freed hist_data. The bug is reproducible from userspace by writing three hist triggers to tracefs: cd /sys/kernel/tracing echo 'hist:keys=common_pid:x=common_pid:name=mh' > events/sched/sched_switch/trigger echo 'hist:keys=common_pid:x=common_pid:name=mh' > events/sched/sched_process_fork/trigger echo 'hist:keys=common_pid:vals=$x' > events/sched/sched_process_exit/trigger The third write panics the kernel: BUG: KASAN: slab-use-after-free in find_var_file.part.0+0x272/0x290 Read of size 8 at addr ffff888001f8a0e0 by task sh/1 CPU: 1 UID: 0 PID: 1 Comm: sh Tainted: G D N Call Trace: find_var_file.part.0 find_event_var parse_atom parse_expr __create_val_field event_hist_trigger_parse trigger_process_regex event_trigger_write vfs_write ksys_write do_syscall_64 entry_SYSCALL_64_after_hwframe Allocated by task 1: event_hist_trigger_parse Freed by task 1: hist_register_trigger+0x618/0xa30 event_hist_trigger_parse The buggy address belongs to freed 2048-byte region Oops: general protection fault ... RIP: find_var_file.part.0 Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b Fix by removing the hist_data from tr->hist_vars and releasing the trace_array reference in the named-data branch of hist_register_trigger() before freeing the hist_data.
References
Impacted products
Vendor Product Version
Linux Linux Version: 5ae1b18f05ee2b849dc03b6c15d7da0c1c6efa77
Version: 43b254d46c740bf9dbe65709afa021dd726dfa99
Version: 435d2964af815aae456db554c62963b4515f19d0
Version: 6f86bdeab633a56d5c6dccf1a2c5989b6a5e323e
Version: 6f86bdeab633a56d5c6dccf1a2c5989b6a5e323e
Version: 6f86bdeab633a56d5c6dccf1a2c5989b6a5e323e
Version: f1ae50cfb818ce1ac7a674406dfadb7653e2552d
Version: 6.1.130   ≤
Version: 6.6.81   ≤
Version: 6.12.18   ≤
Version: 6.13.6   ≤
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{
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix use-after-free with same-name named triggers\n\nWhen two hist triggers on different events are registered with the same\nname=, the second one reuses the first as named_data.  Both are added to\ntr-\u003ehist_vars by save_hist_vars() during event_hist_trigger_parse(),\nbecause save_hist_vars() is called before event_trigger_register() while\nthe named reuse is only detected later, in hist_register_trigger().\n\nIn the named-data branch hist_register_trigger() then frees the second\nhistogram\u0027s hist_data via destroy_hist_data(), but never removes its\ntr-\u003ehist_vars list entry, leaving a dangling pointer and leaking the\ntrace_array reference it holds.\n\nA later hist trigger that references a variable makes find_var_file()\nwalk tr-\u003ehist_vars and dereference the freed hist_data.  The bug is\nreproducible from userspace by writing three hist triggers to tracefs:\n\n  cd /sys/kernel/tracing\n  echo \u0027hist:keys=common_pid:x=common_pid:name=mh\u0027 \u003e events/sched/sched_switch/trigger\n  echo \u0027hist:keys=common_pid:x=common_pid:name=mh\u0027 \u003e events/sched/sched_process_fork/trigger\n  echo \u0027hist:keys=common_pid:vals=$x\u0027 \u003e events/sched/sched_process_exit/trigger\n\nThe third write panics the kernel:\n\n  BUG: KASAN: slab-use-after-free in find_var_file.part.0+0x272/0x290\n  Read of size 8 at addr ffff888001f8a0e0 by task sh/1\n  CPU: 1 UID: 0 PID: 1 Comm: sh Tainted: G      D          N\n  Call Trace:\n    find_var_file.part.0\n    find_event_var\n    parse_atom\n    parse_expr\n    __create_val_field\n    event_hist_trigger_parse\n    trigger_process_regex\n    event_trigger_write\n    vfs_write\n    ksys_write\n    do_syscall_64\n    entry_SYSCALL_64_after_hwframe\n  Allocated by task 1:\n    event_hist_trigger_parse\n  Freed by task 1:\n    hist_register_trigger+0x618/0xa30\n    event_hist_trigger_parse\n  The buggy address belongs to freed 2048-byte region\n  Oops: general protection fault ... RIP: find_var_file.part.0\n  Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b\n\nFix by removing the hist_data from tr-\u003ehist_vars and releasing the\ntrace_array reference in the named-data branch of hist_register_trigger()\nbefore freeing the hist_data."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The UAF is reached only by writing hist trigger commands to tracefs event trigger files via write(2) (event_trigger_write -\u003e event_hist_trigger_parse). There is no network, adjacent-radio, or physical-device path into hist_register_trigger() or find_var_file().\nAC:L - Triggering is fully deterministic: two sequential same-name named hist writes free hist_data while leaving it on tr-\u003ehist_vars, and a third vals=$x write walks that dangling pointer. No race or victim state is required, and CONFIG_HIST_TRIGGERS is standard in distro and Android kernels.\nPR:L - The path has no capable() check; event_trigger_open() only enforces LOCKDOWN_TRACEFS and DAC (TRACE_MODE_WRITE 0640). Tracefs is routinely delegated to non-root tracing users (Android/Perfetto, ChromeOS debugd, gid= tracing mounts), matching prior named-hist UAF scores (CVE-2025-21899).\nUI:N - The attacker performs all three trigger writes themselves; no victim action, mount, or cooperating process is required.\nS:U - The slab use-after-free corrupts kernel heap objects in the tracing subsystem within the same OS security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - find_var_file() and find_var_field() dereference the freed 2048-byte hist_trigger_data (event_file, fields[]). After reclaiming that slab, the attacker controls those pointers, and create_var_ref() persists var_field-\u003ehist_data for later tracing_map reads, yielding an arbitrary kernel read primitive.\nI:H - The dangling hist_vars entry plus a sprayed hist_trigger_data lets create_var_ref() store attacker-controlled hist_data/map pointers into the new trigger; event_hist_trigger()/resolve_var_refs() then write tracing_map state through those pointers, a heap write primitive suitable for control-flow hijack.\nA:H - The commit reproduces a KASAN slab-use-after-free in find_var_file() that oopses or panics the kernel (including killing init). Any use-after-free of hist_data is a reliable whole-system crash even without successful exploitation."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:52:00.175Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/441aa6742dff70297b5f64533a07a6189a026e91"
        },
        {
          "url": "https://git.kernel.org/stable/c/3a8534664426c071c2dfb5b4ffa36b18a2abfd79"
        },
        {
          "url": "https://git.kernel.org/stable/c/477d762be4b0ffaf01429ccd88859e93b0ec28cc"
        },
        {
          "url": "https://git.kernel.org/stable/c/b1a49c22de01faf176d44e5caa765e237353a579"
        },
        {
          "url": "https://git.kernel.org/stable/c/83d1ae0406d8eade219a81b401e201702dd9dc55"
        },
        {
          "url": "https://git.kernel.org/stable/c/a7318172aa332a161fb9618286e64454c827f8fd"
        }
      ],
      "title": "tracing: Fix use-after-free with same-name named triggers",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89746",
    "datePublished": "2026-09-11T19:46:51.529Z",
    "dateReserved": "2026-09-11T19:38:34.762Z",
    "dateUpdated": "2026-10-19T08:52:00.175Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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