GHSA-MHC7-JMQ5-GH86
Vulnerability from github – Published: 2026-08-15 15:30 – Updated: 2026-08-15 15:30In the Linux kernel, the following vulnerability has been resolved:
ALSA: seq: Fix division by zero in initialize_timer()
A userspace-driven ALSA timer (SND_UTIMER) lets an unprivileged user set the backing snd_timer's hardware resolution to an arbitrary 64-bit value via SNDRV_TIMER_IOCTL_CREATE. snd_utimer_create() only rejects zero.
When such a timer is bound to a sequencer queue, initialize_timer() computes the tick period as
tmr->ticks = 1000000000 / (r * freq);
where r is that user-controlled resolution and freq is the sequencer update rate in Hz, clamped to MIN_FREQUENCY..MAX_FREQUENCY (10..6250). A resolution of 2^63 makes the 64-bit product r * freq wrap to zero for any even freq, including DEFAULT_FREQUENCY (1000), so the division faults with a divide-by-zero.
The division runs under tmr->lock with interrupts disabled, so the oops leaves the spinlock held and hangs the CPU. It is reachable by an unprivileged user with access to /dev/snd/timer and /dev/snd/seq.
Oops: divide error: 0000 [#1] SMP KASAN PTI CPU: 7 UID: 1000 PID: 456 Comm: alsa_seq_utimer Not tainted 7.2.0-rc4+ RIP: 0010:initialize_timer.constprop.0+0x20a/0x2d0 snd_seq_timer_start+0x15e/0x2b0 snd_seq_control_queue+0x56f/0xba0 snd_seq_write+0x3e0/0x730
Reject an overflowing product with check_mul_overflow() and fall back to a single tick, which also avoids feeding a wrapped-but-nonzero divisor (e.g. 2^63 * 1000 mod 2^64 == 0, or other resolutions wrapping to a small value) into the period computation.
{
"affected": [],
"aliases": [
"CVE-2026-74504"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T13:17:55Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: Fix division by zero in initialize_timer()\n\nA userspace-driven ALSA timer (SND_UTIMER) lets an unprivileged user set\nthe backing snd_timer\u0027s hardware resolution to an arbitrary 64-bit value\nvia SNDRV_TIMER_IOCTL_CREATE. snd_utimer_create() only rejects zero.\n\nWhen such a timer is bound to a sequencer queue, initialize_timer()\ncomputes the tick period as\n\n\ttmr-\u003eticks = 1000000000 / (r * freq);\n\nwhere r is that user-controlled resolution and freq is the sequencer\nupdate rate in Hz, clamped to MIN_FREQUENCY..MAX_FREQUENCY (10..6250).\nA resolution of 2^63 makes the 64-bit product r * freq wrap to zero for\nany even freq, including DEFAULT_FREQUENCY (1000), so the division faults\nwith a divide-by-zero.\n\nThe division runs under tmr-\u003elock with interrupts disabled, so the oops\nleaves the spinlock held and hangs the CPU. It is reachable by an\nunprivileged user with access to /dev/snd/timer and /dev/snd/seq.\n\n Oops: divide error: 0000 [#1] SMP KASAN PTI\n CPU: 7 UID: 1000 PID: 456 Comm: alsa_seq_utimer Not tainted 7.2.0-rc4+\n RIP: 0010:initialize_timer.constprop.0+0x20a/0x2d0\n snd_seq_timer_start+0x15e/0x2b0\n snd_seq_control_queue+0x56f/0xba0\n snd_seq_write+0x3e0/0x730\n\nReject an overflowing product with check_mul_overflow() and fall back to\na single tick, which also avoids feeding a wrapped-but-nonzero divisor\n(e.g. 2^63 * 1000 mod 2^64 == 0, or other resolutions wrapping to a small\nvalue) into the period computation.",
"id": "GHSA-mhc7-jmq5-gh86",
"modified": "2026-08-15T15:30:34Z",
"published": "2026-08-15T15:30:34Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74504"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/21e19688433452dfbbbe6b2bb670dea6eb92f0f6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/42c6543ff27ea280334244458d4f52ec7133cc05"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5260e195c53e898a4a76527d4bb2178f31795e78"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d0e19932875746118e298b4c974f3b2d4aeb16fc"
}
],
"schema_version": "1.4.0",
"severity": []
}
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.
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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.