CVE-2026-68202 (GCVE-0-2026-68202)
Vulnerability from cvelistv5
Published
2026-08-10 12:00
Modified
2026-08-23 12:46
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
ALSA: seq: close a re-opened queue timer in the destructor
queue_delete() closes the queue timer, then frees it. snd_seq_timer_close()
clears q->timer->timeri. snd_use_lock_sync() then drains borrowers, and
snd_seq_timer_delete() frees q->timer.
A borrower can re-open the timer inside that window. A SET_QUEUE_CLIENT
that took a queueptr() use_lock reference before the queue was unlinked
runs snd_seq_timer_open() after the close. Open refuses re-open only while
timeri is set, and the close just cleared it, so it re-opens timeri.
snd_seq_timer_delete() does not close that instance. Its snd_seq_timer_stop()
is a no-op, because running was cleared first. So it frees q->timer with the
instance still live. The queue is freed next.
The instance stays on the global timer with callback_data pointing at the
freed queue. A non-owner START on the unlocked queue arms it. The next tick
derefs the freed queue in snd_seq_timer_interrupt().
Reachable by an unprivileged user with access to /dev/snd/seq. No CAP and
no queue ownership required.
Close any lingering instance in the destructor. There, ->timeri can no
longer change: the queue is unlinked and all use_lock borrowers have
drained, so no snd_seq_queue_use() can re-open it. Close it before clearing
q->timer. snd_timer_close() waits for any in-flight snd_seq_timer_interrupt()
to finish, and that callback still reads q->timer (via snd_seq_check_queue()),
so q->timer must stay valid until it drains.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 |
||
{
"containers": {
"cna": {
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{
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"product": "Linux",
"programFiles": [
"sound/core/seq/seq_timer.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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{
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"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": "5.10.*",
"status": "unaffected",
"version": "5.10.266",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.217",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.148",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.101",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.42",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
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}
],
"negate": false,
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: close a re-opened queue timer in the destructor\n\nqueue_delete() closes the queue timer, then frees it. snd_seq_timer_close()\nclears q-\u003etimer-\u003etimeri. snd_use_lock_sync() then drains borrowers, and\nsnd_seq_timer_delete() frees q-\u003etimer.\n\nA borrower can re-open the timer inside that window. A SET_QUEUE_CLIENT\nthat took a queueptr() use_lock reference before the queue was unlinked\nruns snd_seq_timer_open() after the close. Open refuses re-open only while\ntimeri is set, and the close just cleared it, so it re-opens timeri.\n\nsnd_seq_timer_delete() does not close that instance. Its snd_seq_timer_stop()\nis a no-op, because running was cleared first. So it frees q-\u003etimer with the\ninstance still live. The queue is freed next.\n\nThe instance stays on the global timer with callback_data pointing at the\nfreed queue. A non-owner START on the unlocked queue arms it. The next tick\nderefs the freed queue in snd_seq_timer_interrupt().\n\nReachable by an unprivileged user with access to /dev/snd/seq. No CAP and\nno queue ownership required.\n\nClose any lingering instance in the destructor. There, -\u003etimeri can no\nlonger change: the queue is unlinked and all use_lock borrowers have\ndrained, so no snd_seq_queue_use() can re-open it. Close it before clearing\nq-\u003etimer. snd_timer_close() waits for any in-flight snd_seq_timer_interrupt()\nto finish, and that callback still reads q-\u003etimer (via snd_seq_check_queue()),\nso q-\u003etimer must stay valid until it drains."
}
],
"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 bug is reached through ioctls on the local character device /dev/snd/seq (SNDRV_SEQ_IOCTL_CREATE_QUEUE/DELETE_QUEUE/SET_QUEUE_CLIENT); no network or adjacent-network path exists to the ALSA sequencer.\nAC:L - The attacker controls both sides of the race \u2014 one thread deletes the queue while another spins on SET_QUEUE_CLIENT holding a queueptr() reference \u2014 and can retry the loop indefinitely on a default kernel with CONFIG_SND_SEQUENCER, so the window is reliably hit.\nPR:L - Only an unprivileged local user able to open /dev/snd/seq is needed; snd_seq_queue_use() performs no owner or access check and no capability is required, as the fix commit states explicitly.\nUI:N - The attacker\u0027s own threads create, delete and re-use the queue and the global system timer fires on its own; no victim action is involved.\nS:U - The use-after-free corrupts kernel heap objects within the same kernel security authority, giving at most kernel privilege escalation rather than crossing a VM, IOMMU or sandbox boundary.\nC:H - The stale timer instance dereferences the freed snd_seq_queue and snd_seq_timer, reading tick/time fields and freed prioq pointers that can be reclaimed by attacker-sprayed objects, giving a route to disclose arbitrary kernel memory.\nI:H - snd_seq_timer_interrupt() writes cur_time, tick and last_update into the freed snd_seq_timer slab and snd_seq_check_queue() dispatches events through freed queue pointers, yielding a controllable write primitive on reclaimed heap memory suitable for privilege escalation.\nA:H - Even unexploited, the timer callback derefs freed memory and takes a spinlock in a freed object from interrupt context, causing oops, lock corruption or panic \u2014 a repeatable denial of service for any local user."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-23T12:46:08.116Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/b7feeaca1f53b10df9b4de9eaf611767ca70dc92"
},
{
"url": "https://git.kernel.org/stable/c/7478ef94b49bc9789cf1a003deec58b42283dde4"
},
{
"url": "https://git.kernel.org/stable/c/9d9be6fc30f384f92c4e1b8ed40bd9d4796b7833"
},
{
"url": "https://git.kernel.org/stable/c/fb40d03ed792a8a8bf77aa0ee15df57b0ff78b07"
},
{
"url": "https://git.kernel.org/stable/c/24f0cabf173539f048946c8fc221131dc221f277"
},
{
"url": "https://git.kernel.org/stable/c/6a10025c7fd09a7d2af37a3ae1da188569fce470"
},
{
"url": "https://git.kernel.org/stable/c/31a6163e301d832060f8236f1ed17cbc1ca198df"
},
{
"url": "https://git.kernel.org/stable/c/2c4dc0ed50b05cd847a4b34b8cebf0775f19aeb9"
}
],
"title": "ALSA: seq: close a re-opened queue timer in the destructor",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-68202",
"datePublished": "2026-08-10T12:00:21.279Z",
"dateReserved": "2026-07-30T09:28:09.374Z",
"dateUpdated": "2026-08-23T12:46:08.116Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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