FKIE_CVE-2026-74388
Vulnerability from fkie_nvd - Published: 2026-08-15 06:22 - Updated: 2026-08-17 06:19
Severity
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 (?:?)
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"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"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"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 (?:?)"
}
],
"id": "CVE-2026-74388",
"lastModified": "2026-08-17T06:19:33.820",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-08-15T06:22:40.733",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/6dc781778b595be94c31395b2cb167f65145d91f"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/7aad70cabd8f34cf11a9593fcd3f2ac3f5496943"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/7c349b4f2a603202fb8c363bd2774a22ac2fddf3"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
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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.
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.
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