CVE-2026-74387

Estado: RecibidaAlta (7.8)—

In the Linux kernel, the following vulnerability has been resolved:

ALSA: seq: midi: Serialize output teardown with event_input

event_process_midi() borrows msynth->output_rfile.output and then passes the substream to dump_midi() and snd_rawmidi_kernel_write() without synchronizing with the output open/close transition. midisynth_use() also publishes output_rfile before snd_rawmidi_output_params() has finished.

The last midisynth_unuse() can therefore release the same rawmidi file and free substream->runtime before snd_rawmidi_kernel_write1() takes its runtime buffer reference. That leaves the event_input path using a stale substream or runtime and can end in a NULL-deref or use-after-free.

Leer descripción completaMostrar menos

Fix this with two pieces of synchronization. Keep a short IRQ-safe spinlock only for publishing or clearing output_rfile and for pairing the output snapshot with an snd_use_lock_t reference. Once event_process_midi() has taken that in-flight reference, it drops the spinlock before calling snd_seq_dump_var_event(), dump_midi(), or snd_rawmidi_kernel_write(). midisynth_unuse() now detaches the visible rawmidi file under the same spinlock, waits for the in-flight writers to drain, and only then drains and releases the saved file. midisynth_use() likewise opens into a local snd_rawmidi_file and publishes it only after snd_rawmidi_output_params() succeeds.

The buggy scenario involves two paths, with each column showing the order within that path:

Detalles técnicos trazas, registros y código del informe original

event_input path:                     last unuse path:
1. event_process_midi() snapshots    1. midisynth_unuse() starts
   output_rfile.output.                 tearing down output_rfile.
2. dump_midi() reaches               2. snd_rawmidi_kernel_release()
   snd_rawmidi_kernel_write()           closes the output file.
   before runtime is pinned.         3. close_substream() frees
3. The callback keeps using             substream->runtime.
   the borrowed substream.

Validation reproduced this kernel report:
KASAN null-ptr-deref in snd_rawmidi_kernel_write1+0x56/0x360
RIP: 0033:0x7fde7dd0837f
RIP: 0010:snd_rawmidi_kernel_write1+0x56/0x360

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 7.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.17%
Percentil entre todas las CVEs puntuadas: 6
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation85 %
Impacto principalT1499.004 Application or System Exploitationimpact75 %
Impacto secundarioT1546 Event Triggered Executionprivilege escalation · persistence60 %

Vulnerabilidad local (AV:L/PR:L) que permite un atacante con privilegios locales causar un NULL-deref o use-after-free en el kernel, resultando en DoN o posible ejecución de código arbitrario mediante race condition en ALSA seq.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Update Software Threat Intelligence Program Privileged Account Management Filter Network Traffic Execution Prevention Application Isolation and Sandboxing

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-74387",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
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      "affectedData": [
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
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          "programFiles": [
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              "version": "0",
              "lessThan": "2.6.12",
              "versionType": "semver"
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            {
              "status": "unaffected",
              "version": "6.1.178",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
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              "status": "unaffected",
              "version": "6.6.145",
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              "version": "6.12.97",
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          "programFiles": [
            "sound/core/seq/seq_midi.c"
          ],
          "defaultStatus": "affected"
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  ],
  "published": "2026-08-15T06:22:40.610",
  "references": [
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      "url": "https://git.kernel.org/stable/c/11165fe2c5ea0516debe486d91df67abbe36905e",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: midi: Serialize output teardown with event_input\n\nevent_process_midi() borrows msynth->output_rfile.output and then\npasses the substream to dump_midi() and snd_rawmidi_kernel_write()\nwithout synchronizing with the output open/close transition.\nmidisynth_use() also publishes output_rfile before\nsnd_rawmidi_output_params() has finished.\n\nThe last midisynth_unuse() can therefore release the same rawmidi file\nand free substream->runtime before snd_rawmidi_kernel_write1() takes\nits runtime buffer reference. That leaves the event_input path using a\nstale substream or runtime and can end in a NULL-deref or use-after-free.\n\nFix this with two pieces of synchronization. Keep a short IRQ-safe\nspinlock only for publishing or clearing output_rfile and for pairing\nthe output snapshot with an snd_use_lock_t reference. Once\nevent_process_midi() has taken that in-flight reference, it drops the\nspinlock before calling snd_seq_dump_var_event(), dump_midi(), or\nsnd_rawmidi_kernel_write(). midisynth_unuse() now detaches the visible\nrawmidi file under the same spinlock, waits for the in-flight writers\nto drain, and only then drains and releases the saved file.\nmidisynth_use() likewise opens into a local snd_rawmidi_file and\npublishes it only after snd_rawmidi_output_params() succeeds.\n\nThe buggy scenario involves two paths, with each column showing the\norder within that path:\n\nevent_input path:                     last unuse path:\n1. event_process_midi() snapshots    1. midisynth_unuse() starts\n   output_rfile.output.                 tearing down output_rfile.\n2. dump_midi() reaches               2. snd_rawmidi_kernel_release()\n   snd_rawmidi_kernel_write()           closes the output file.\n   before runtime is pinned.         3. close_substream() frees\n3. The callback keeps using             substream->runtime.\n   the borrowed substream.\n\nValidation reproduced this kernel report:\nKASAN null-ptr-deref in snd_rawmidi_kernel_write1+0x56/0x360\nRIP: 0033:0x7fde7dd0837f\nRIP: 0010:snd_rawmidi_kernel_write1+0x56/0x360"
    }
  ],
  "lastModified": "2026-08-17T06:19:33.670",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}