CVE-2026-90207 (GCVE-0-2026-90207)
Vulnerability from cvelistv5
Published
2026-09-17 16:07
Modified
2026-10-19 08:59
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: ALSA: seq: midi: Serialize input teardown with event_input snd_midi_input_event() must not be running while a rawmidi substream is closing, since this can lead to the trigger state becoming out-of-step through this sequence in snd_rawmidi_input_trigger(): snd_rawmidi_input_trigger(up=0) snd_midi_input_event() -> snd_rawmidi_kernel_read() -> snd_rawmidi_input_trigger(up=1) -> cancel_work_sync() which ends with the underlying device being active unexpectedly. When this is called from close_substream(), further input can re-trigger the input event leaving it running after rawmidi_release_priv() has set rfile->rmidi to NULL which leads to: Unable to handle kernel NULL pointer dereference at virtual address 00000000000000b0 Call trace: snd_midi_input_event+0x3c/0x134 [snd_seq_midi] (P) snd_rawmidi_input_event_work+0x1c/0x2c process_one_work+0x150/0x3a4 worker_thread+0x190/0x318 Apply a similar approach to commit ef7607ab1c8ad ("ALSA: seq: midi: Serialize output teardown with event_input") which fixed the same issue in the output direction, but updated to use RCU following Takashi Iwai's proposed follow-on patch [1]. With this change in place, midisynth_unsubscribe() clears the input file so snd_midi_input_event() will not re-trigger the stream and will be quiesced by the cancel_work_sync() in snd_rawmidi_input_trigger(). [1] https://lore.kernel.org/linux-sound/20260813144224.753399-1-tiwai@suse.de/
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "sound/core/seq/seq_midi.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "sound/core/seq/seq_midi.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "0",
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              "version": "6.1.188",
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              "version": "6.6.157",
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              "status": "unaffected",
              "version": "6.12.110",
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.188",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.157",
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: midi: Serialize input teardown with event_input\n\nsnd_midi_input_event() must not be running while a rawmidi substream is\nclosing, since this can lead to the trigger state becoming out-of-step\nthrough this sequence in snd_rawmidi_input_trigger():\n\n\tsnd_rawmidi_input_trigger(up=0)\n\t\t\t\t\tsnd_midi_input_event()\n\t\t\t\t\t -\u003e snd_rawmidi_kernel_read()\n\t\t\t\t\t     -\u003e snd_rawmidi_input_trigger(up=1)\n\t  -\u003e cancel_work_sync()\n\nwhich ends with the underlying device being active unexpectedly.\n\nWhen this is called from close_substream(), further input can re-trigger\nthe input event leaving it running after rawmidi_release_priv() has set\nrfile-\u003ermidi to NULL which leads to:\n\n\tUnable to handle kernel NULL pointer dereference at virtual address 00000000000000b0\n\tCall trace:\n\t snd_midi_input_event+0x3c/0x134 [snd_seq_midi] (P)\n\t snd_rawmidi_input_event_work+0x1c/0x2c\n\t process_one_work+0x150/0x3a4\n\t worker_thread+0x190/0x318\n\nApply a similar approach to commit ef7607ab1c8ad (\"ALSA: seq: midi:\nSerialize output teardown with event_input\") which fixed the same issue\nin the output direction, but updated to use RCU following Takashi Iwai\u0027s\nproposed follow-on patch [1].\n\nWith this change in place, midisynth_unsubscribe() clears the input file\nso snd_midi_input_event() will not re-trigger the stream and will be\nquiesced by the cancel_work_sync() in snd_rawmidi_input_trigger().\n\n[1] https://lore.kernel.org/linux-sound/20260813144224.753399-1-tiwai@suse.de/"
        }
      ],
      "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 race is reached from a local sequencer client: snd_seq_open() on /dev/snd/seq, SNDRV_SEQ_IOCTL_SUBSCRIBE_PORT (midisynth_subscribe) to open the rawmidi input, then SNDRV_SEQ_IOCTL_UNSUBSCRIBE_PORT or client close (midisynth_unsubscribe -\u003e snd_rawmidi_kernel_release). Bytes that schedule snd_midi_input_event come from the bound rawmidi device, not a network or radio protocol.\nAC:L - The attacker owns teardown (last unsubscribe/close) and starts input by subscribing: midisynth_subscribe sets runtime-\u003eevent to snd_midi_input_event and snd_rawmidi_kernel_read() triggers the device. Concurrent snd_midi_input_event can re-call snd_rawmidi_input_trigger(up=1) during close_substream\u0027s trigger(up=0)/cancel_work_sync window. Repeating subscribe/unsubscribe on that live port makes the race retryable.\nPR:L - snd_seq_open() has no capable() check. check_subscription_permission() allows any sequencer client to subscribe to seq_midi ports because they advertise SNDRV_SEQ_PORT_CAP_READ|SNDRV_SEQ_PORT_CAP_SUBS_READ. Typical DAC on /dev/snd/seq is audio-group/uaccess, so an unprivileged local user suffices; init-namespace root is not required.\nUI:N - The attacker opens their own /dev/snd/seq client, creates a destination port, issues SNDRV_SEQ_IOCTL_SUBSCRIBE_PORT to a seq_midi input port, and then unsubscribes or closes to run midisynth_unsubscribe. No other user must mount, click, or open a file.\nS:U - The UAF/NULL deref is in kernel rawmidi lifetime (close_substream/snd_rawmidi_runtime_free versus snd_rawmidi_input_event_work calling snd_midi_input_event). That is local kernel memory corruption in the same OS authority, not a VM, IOMMU, or sandbox escape.\nC:H - After cancel_work_sync, a re-triggered device can schedule runtime-\u003eevent_work; close_substream then kfree()s snd_rawmidi_runtime while the work later does container_of() and calls runtime-\u003eevent. Use-after-free of that heap object enables arbitrary reads via heap reuse of the freed runtime.\nI:H - The freed snd_rawmidi_runtime embeds event_work and the runtime-\u003eevent function pointer that snd_rawmidi_input_event_work invokes. Heap spraying that object lets an attacker hijack the callback for arbitrary kernel write or control-flow hijack, not merely a one-shot crash.\nA:H - The reported crash is a NULL deref in snd_midi_input_event from snd_rawmidi_input_event_work after rawmidi_release_priv() nulls the file and close_substream frees runtime, which oopses the kernel and can be retried with subscribe/unsubscribe cycles."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:59:43.508Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/de76a2b47582cd6dba2e15f024681bf377ecc94a"
        },
        {
          "url": "https://git.kernel.org/stable/c/89d986897aff7275b42e075e556731b8353366af"
        },
        {
          "url": "https://git.kernel.org/stable/c/6290afaae54c7a9fa3bca3b4d5433e6d83e8669d"
        },
        {
          "url": "https://git.kernel.org/stable/c/210c193a9ef1312fab153948c6928e4cfaa1f03b"
        },
        {
          "url": "https://git.kernel.org/stable/c/282a3ef9e4b63b2f6823bbbb3c1a90b002cdaf12"
        },
        {
          "url": "https://git.kernel.org/stable/c/403f7f3ad3808a0096d84cf228fab68dc253fd9d"
        }
      ],
      "title": "ALSA: seq: midi: Serialize input teardown with event_input",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90207",
    "datePublished": "2026-09-17T16:07:22.825Z",
    "dateReserved": "2026-09-11T19:38:34.793Z",
    "dateUpdated": "2026-10-19T08:59:43.508Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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