Vulnerability-Lookup

GHSA-QR2G-FP68-M7Q5

Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33

Details

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

ALSA: seq: oss: Fix UAF at handling events with embedded SysEx data

The OSS sequencer processes the input MIDI bytes into a sequencer event to be dispatched later (in snd_seq_oss_midi_putc() called from snd_seq_oss_process_event()). When it's a SysEx data, the event record contains data.ext.ptr pointer to the original SysEx bytes, and the referred data is copied into the pool afterwards at dispatching. The problem is that, if the sequencer port gets closed concurrently before the dispatch, the OSS sequencer core also releases the resources (in snd_seq_oss_midi_check_exit_port()), while the pending event may hold a stale pointer, eventually leading to a UAF at a later dispatch.

Fortunately, there is already a refcounting mechanism (snd_use_lock_t) for the OSS MIDI device access, and for addressing the issue above, we just need to extend the refcount until the event gets dispatched.

This patch extends snd_seq_oss_process_event() to give back the refcount object, which is in turn released after calling the sequencer dispatcher with the given event in the caller side.

According to the original report, KASAN report as below:

KASAN slab-use-after-free in snd_seq_event_dup+0x40c/0x470 RIP: 0033:0x7f2cb66a6340 Read of size 6 Call trace: dump_stack_lvl+0x73/0xb0 (?:?) print_report+0xd1/0x650 (?:?) srso_alias_return_thunk+0x5/0xfbef5 (?:?) __virt_addr_valid+0x1a7/0x340 (?:?) kasan_complete_mode_report_info+0x64/0x200 (?:?) kasan_report+0xf7/0x130 (?:?) snd_seq_event_dup+0x40c/0x470 (?:?) kasan_check_range+0x10c/0x1c0 (?:?) __asan_memcpy+0x27/0x70 (?:?) snd_seq_event_dup+0x9/0x470 (?:?) snd_seq_client_enqueue_event+0x139/0x240 (?:?) _raw_spin_unlock_irqrestore+0x4b/0x60 (?:?) snd_seq_kernel_client_enqueue+0x102/0x120 (?:?) snd_seq_oss_write+0x416/0x4e0 (?:?) apparmor_file_permission+0x20/0x30 (?:?) odev_write+0x3b/0x60 (?:?) vfs_write+0x1ce/0x850 (?:?) lock_release+0xc8/0x2a0 (?:?) __kasan_check_write+0x18/0x20 (?:?) __mutex_unlock_slowpath+0x129/0x510 (?:?) ksys_write+0xe1/0x180 (?:?) mutex_unlock+0x16/0x20 (?:?) odev_ioctl+0x65/0xc0 (?:?) __x64_sys_write+0x46/0x60 (?:?) x64_sys_call+0x7d/0x20d0 (?:?) do_syscall_64+0xc1/0x360 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)

Severity

7.8 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-74388"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-15T06:22:40Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: oss: Fix UAF at handling events with embedded SysEx data\n\nThe OSS sequencer processes the input MIDI bytes into a sequencer\nevent to be dispatched later (in snd_seq_oss_midi_putc() called from\nsnd_seq_oss_process_event()).  When it\u0027s a SysEx data, the event\nrecord contains data.ext.ptr pointer to the original SysEx bytes, and\nthe referred data is copied into the pool afterwards at dispatching.\nThe problem is that, if the sequencer port gets closed concurrently\nbefore the dispatch, the OSS sequencer core also releases the\nresources (in snd_seq_oss_midi_check_exit_port()), while the pending\nevent may hold a stale pointer, eventually leading to a UAF at a later\ndispatch.\n\nFortunately, there is already a refcounting mechanism (snd_use_lock_t)\nfor the OSS MIDI device access, and for addressing the issue above, we\njust need to extend the refcount until the event gets dispatched.\n\nThis patch extends snd_seq_oss_process_event() to give back the\nrefcount object, which is in turn released after calling the sequencer\ndispatcher with the given event in the caller side.\n\nAccording to the original report, KASAN report as below:\n\nKASAN slab-use-after-free in snd_seq_event_dup+0x40c/0x470\nRIP: 0033:0x7f2cb66a6340\nRead of size 6\nCall trace:\n  dump_stack_lvl+0x73/0xb0 (?:?)\n  print_report+0xd1/0x650 (?:?)\n  srso_alias_return_thunk+0x5/0xfbef5 (?:?)\n  __virt_addr_valid+0x1a7/0x340 (?:?)\n  kasan_complete_mode_report_info+0x64/0x200 (?:?)\n  kasan_report+0xf7/0x130 (?:?)\n  snd_seq_event_dup+0x40c/0x470 (?:?)\n  kasan_check_range+0x10c/0x1c0 (?:?)\n  __asan_memcpy+0x27/0x70 (?:?)\n  snd_seq_event_dup+0x9/0x470 (?:?)\n  snd_seq_client_enqueue_event+0x139/0x240 (?:?)\n  _raw_spin_unlock_irqrestore+0x4b/0x60 (?:?)\n  snd_seq_kernel_client_enqueue+0x102/0x120 (?:?)\n  snd_seq_oss_write+0x416/0x4e0 (?:?)\n  apparmor_file_permission+0x20/0x30 (?:?)\n  odev_write+0x3b/0x60 (?:?)\n  vfs_write+0x1ce/0x850 (?:?)\n  lock_release+0xc8/0x2a0 (?:?)\n  __kasan_check_write+0x18/0x20 (?:?)\n  __mutex_unlock_slowpath+0x129/0x510 (?:?)\n  ksys_write+0xe1/0x180 (?:?)\n  mutex_unlock+0x16/0x20 (?:?)\n  odev_ioctl+0x65/0xc0 (?:?)\n  __x64_sys_write+0x46/0x60 (?:?)\n  x64_sys_call+0x7d/0x20d0 (?:?)\n  do_syscall_64+0xc1/0x360 (arch/x86/entry/syscall_64.c:87)\n  entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)",
  "id": "GHSA-qr2g-fp68-m7q5",
  "modified": "2026-08-17T06:33:42Z",
  "published": "2026-08-15T06:32:32Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74388"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6dc781778b595be94c31395b2cb167f65145d91f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7aad70cabd8f34cf11a9593fcd3f2ac3f5496943"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7c349b4f2a603202fb8c363bd2774a22ac2fddf3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-74388 (GCVE-0-2026-74388)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:59 – Updated: 2026-08-17 05:46

Title

ALSA: seq: oss: Fix UAF at handling events with embedded SysEx data

Summary

In the Linux kernel, the following vulnerability has been resolved: ALSA: seq: oss: Fix UAF at handling events with embedded SysEx data The OSS sequencer processes the input MIDI bytes into a sequencer event to be dispatched later (in snd_seq_oss_midi_putc() called from snd_seq_oss_process_event()). When it's a SysEx data, the event record contains data.ext.ptr pointer to the original SysEx bytes, and the referred data is copied into the pool afterwards at dispatching. The problem is that, if the sequencer port gets closed concurrently before the dispatch, the OSS sequencer core also releases the resources (in snd_seq_oss_midi_check_exit_port()), while the pending event may hold a stale pointer, eventually leading to a UAF at a later dispatch. Fortunately, there is already a refcounting mechanism (snd_use_lock_t) for the OSS MIDI device access, and for addressing the issue above, we just need to extend the refcount until the event gets dispatched. This patch extends snd_seq_oss_process_event() to give back the refcount object, which is in turn released after calling the sequencer dispatcher with the given event in the caller side. According to the original report, KASAN report as below: KASAN slab-use-after-free in snd_seq_event_dup+0x40c/0x470 RIP: 0033:0x7f2cb66a6340 Read of size 6 Call trace: dump_stack_lvl+0x73/0xb0 (?:?) print_report+0xd1/0x650 (?:?) srso_alias_return_thunk+0x5/0xfbef5 (?:?) __virt_addr_valid+0x1a7/0x340 (?:?) kasan_complete_mode_report_info+0x64/0x200 (?:?) kasan_report+0xf7/0x130 (?:?) snd_seq_event_dup+0x40c/0x470 (?:?) kasan_check_range+0x10c/0x1c0 (?:?) __asan_memcpy+0x27/0x70 (?:?) snd_seq_event_dup+0x9/0x470 (?:?) snd_seq_client_enqueue_event+0x139/0x240 (?:?) _raw_spin_unlock_irqrestore+0x4b/0x60 (?:?) snd_seq_kernel_client_enqueue+0x102/0x120 (?:?) snd_seq_oss_write+0x416/0x4e0 (?:?) apparmor_file_permission+0x20/0x30 (?:?) odev_write+0x3b/0x60 (?:?) vfs_write+0x1ce/0x850 (?:?) lock_release+0xc8/0x2a0 (?:?) __kasan_check_write+0x18/0x20 (?:?) __mutex_unlock_slowpath+0x129/0x510 (?:?) ksys_write+0xe1/0x180 (?:?) mutex_unlock+0x16/0x20 (?:?) odev_ioctl+0x65/0xc0 (?:?) __x64_sys_write+0x46/0x60 (?:?) x64_sys_call+0x7d/0x20d0 (?:?) do_syscall_64+0xc1/0x360 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/6dc781778b595be94…
https://git.kernel.org/stable/c/7aad70cabd8f34cf1…
https://git.kernel.org/stable/c/7c349b4f2a603202f…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 6dc781778b595be94c31395b2cb167f65145d91f (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 7aad70cabd8f34cf11a9593fcd3f2ac3f5496943 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 7c349b4f2a603202fb8c363bd2774a22ac2fddf3 (git)
Linux	Linux	Affected: 2.6.12 Unaffected: 0 , < 2.6.12 (semver) Unaffected: 6.18.40 , ≤ 6.18.* (semver) Unaffected: 7.1.5 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "sound/core/seq/oss/seq_oss_event.c",
            "sound/core/seq/oss/seq_oss_event.h",
            "sound/core/seq/oss/seq_oss_ioctl.c",
            "sound/core/seq/oss/seq_oss_midi.c",
            "sound/core/seq/oss/seq_oss_midi.h",
            "sound/core/seq/oss/seq_oss_rw.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "6dc781778b595be94c31395b2cb167f65145d91f",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "7aad70cabd8f34cf11a9593fcd3f2ac3f5496943",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "7c349b4f2a603202fb8c363bd2774a22ac2fddf3",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "sound/core/seq/oss/seq_oss_event.c",
            "sound/core/seq/oss/seq_oss_event.h",
            "sound/core/seq/oss/seq_oss_ioctl.c",
            "sound/core/seq/oss/seq_oss_midi.c",
            "sound/core/seq/oss/seq_oss_midi.h",
            "sound/core/seq/oss/seq_oss_rw.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
            {
              "lessThan": "2.6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.40",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.40",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.5",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: oss: Fix UAF at handling events with embedded SysEx data\n\nThe OSS sequencer processes the input MIDI bytes into a sequencer\nevent to be dispatched later (in snd_seq_oss_midi_putc() called from\nsnd_seq_oss_process_event()).  When it\u0027s a SysEx data, the event\nrecord contains data.ext.ptr pointer to the original SysEx bytes, and\nthe referred data is copied into the pool afterwards at dispatching.\nThe problem is that, if the sequencer port gets closed concurrently\nbefore the dispatch, the OSS sequencer core also releases the\nresources (in snd_seq_oss_midi_check_exit_port()), while the pending\nevent may hold a stale pointer, eventually leading to a UAF at a later\ndispatch.\n\nFortunately, there is already a refcounting mechanism (snd_use_lock_t)\nfor the OSS MIDI device access, and for addressing the issue above, we\njust need to extend the refcount until the event gets dispatched.\n\nThis patch extends snd_seq_oss_process_event() to give back the\nrefcount object, which is in turn released after calling the sequencer\ndispatcher with the given event in the caller side.\n\nAccording to the original report, KASAN report as below:\n\nKASAN slab-use-after-free in snd_seq_event_dup+0x40c/0x470\nRIP: 0033:0x7f2cb66a6340\nRead of size 6\nCall trace:\n  dump_stack_lvl+0x73/0xb0 (?:?)\n  print_report+0xd1/0x650 (?:?)\n  srso_alias_return_thunk+0x5/0xfbef5 (?:?)\n  __virt_addr_valid+0x1a7/0x340 (?:?)\n  kasan_complete_mode_report_info+0x64/0x200 (?:?)\n  kasan_report+0xf7/0x130 (?:?)\n  snd_seq_event_dup+0x40c/0x470 (?:?)\n  kasan_check_range+0x10c/0x1c0 (?:?)\n  __asan_memcpy+0x27/0x70 (?:?)\n  snd_seq_event_dup+0x9/0x470 (?:?)\n  snd_seq_client_enqueue_event+0x139/0x240 (?:?)\n  _raw_spin_unlock_irqrestore+0x4b/0x60 (?:?)\n  snd_seq_kernel_client_enqueue+0x102/0x120 (?:?)\n  snd_seq_oss_write+0x416/0x4e0 (?:?)\n  apparmor_file_permission+0x20/0x30 (?:?)\n  odev_write+0x3b/0x60 (?:?)\n  vfs_write+0x1ce/0x850 (?:?)\n  lock_release+0xc8/0x2a0 (?:?)\n  __kasan_check_write+0x18/0x20 (?:?)\n  __mutex_unlock_slowpath+0x129/0x510 (?:?)\n  ksys_write+0xe1/0x180 (?:?)\n  mutex_unlock+0x16/0x20 (?:?)\n  odev_ioctl+0x65/0xc0 (?:?)\n  __x64_sys_write+0x46/0x60 (?:?)\n  x64_sys_call+0x7d/0x20d0 (?:?)\n  do_syscall_64+0xc1/0x360 (arch/x86/entry/syscall_64.c:87)\n  entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)"
        }
      ],
      "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 via local OSS sequencer character devices (/dev/sequencer, /dev/music) through write(2) or SNDCTL_SEQ_OUTOFBAND ioctl into snd_seq_oss_write(); there is no network, Bluetooth, or physical-device input path to this OSS sequencer code.\nAC:L - The attacker controls both sides of the race: one thread streams SysEx MIDI bytes (SEQ_MIDIPUTC) while another concurrently deletes the backing ALSA sequencer port via /dev/snd/seq or triggers PORT_EXIT teardown, and the window is freely repeatable.\nPR:L - Exploitation requires only a local unprivileged account with access to OSS sequencer and ALSA sequencer device nodes, routinely granted via the audio group or seat ACLs on desktop, studio, and kiosk systems; no capability or init-namespace root is checked on this path.\nUI:N - The attacker\u0027s own process(es) perform the SysEx write and concurrent port-close/delete sequence; no separate victim action such as opening files, mounting filesystems, or plugging in hardware is required beyond the attacker\u0027s own device access.\nS:U - The use-after-free corrupts kernel heap memory within the same kernel security authority, enabling local privilege escalation or denial of service, but does not cross a VM, IOMMU, or sandbox security boundary.\nC:H - This is a slab use-after-free where snd_seq_event_dup() memcpy-reads from a freed MIDI coder buffer (KASAN: read of size 6); UAF on kernel heap objects enables controlled reuse and arbitrary kernel memory disclosure via heap grooming.\nI:H - Freed seq_oss_midi/coder objects can be reallocated and corrupted through continued SysEx traffic, providing standard kernel heap overwrite primitives that can be leveraged for arbitrary write and local privilege escalation.\nA:H - The UAF is observed as a KASAN slab-use-after-free during event enqueue and reliably causes kernel oops or panic on the vulnerable path; even without full exploitation, triggering the bug causes high availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:46:37.644Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/6dc781778b595be94c31395b2cb167f65145d91f"
        },
        {
          "url": "https://git.kernel.org/stable/c/7aad70cabd8f34cf11a9593fcd3f2ac3f5496943"
        },
        {
          "url": "https://git.kernel.org/stable/c/7c349b4f2a603202fb8c363bd2774a22ac2fddf3"
        }
      ],
      "title": "ALSA: seq: oss: Fix UAF at handling events with embedded SysEx data",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74388",
    "datePublished": "2026-08-15T05:59:03.147Z",
    "dateReserved": "2026-08-15T05:44:03.891Z",
    "dateUpdated": "2026-08-17T05:46:37.644Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

GHSA-QR2G-FP68-M7Q5

CVE-2026-74388 (GCVE-0-2026-74388)

Tags

Sightings

Nomenclature