Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
Linux Linux — ALSA: seq: Fix race of snd_seq_timer_open()
AV AC PR UI S C I A CVSS EPSS %ile KEV
L H L N U H H H 7.0 .0024 15.0 —
AFFECTED
Product Versions Fixed
Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – —
Linux 2.6.12 – 5.10.44
TIMELINE
May 21 Reserved by Linux
May 21 Published (CNA: Linux)
Aug 4 RESCORED — CVE-2021-47281 (Linux). CVSS 7.8 → 7 (NVD).
Description
In the Linux kernel, the following vulnerability has been resolved:
ALSA: seq: Fix race of snd_seq_timer_open()
The timer instance per queue is exclusive, and snd_seq_timer_open()
should have managed the concurrent accesses. It looks as if it's
checking the already existing timer instance at the beginning, but
it's not right, because there is no protection, hence any later
concurrent call of snd_seq_timer_open() may override the timer
instance easily. This may result in UAF, as the leftover timer
instance can keep running while the queue itself gets closed, as
spotted by syzkaller recently.
For avoiding the race, add a proper check at the assignment of
tmr->timeri again, and return -EBUSY if it's been already registered.
Lifecycle
Complete event history — 3 events, chronological
| Date | Event | Detail |
| May 21, 2024 | Reserved | Reserved by Linux |
| May 21, 2024 | Published | Published (CNA: Linux) |
| August 4, 2026 | RESCORED | RESCORED — CVE-2021-47281 (Linux). CVSS 7.8 → 7 (NVD). |
Affected
Affected products and packages — 2 rows
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
| Linux | Linux | — | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 | — |
| Linux | Linux | — | 2.6.12 | 5.10.44 |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-47281 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.