How severe is CVE-2026-74387?

CVE-2026-74387 has a CVSS score of 7.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-74387?

CVE-2026-74387 affects the following packages: Kernel (Linux). Ecosystems affected: Linux.

How do I fix CVE-2026-74387?

Update Kernel to 6.1.178 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-74387 is resolved across your whole dependency graph.

How do I detect CVE-2026-74387 in my Linux dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Kernel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2026-74387 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-74387?

O3 pinpoints whether CVE-2026-74387 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2026-74387 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-74387 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was CVE-2026-74387 published, and has it been updated?

CVE-2026-74387 was published on August 15, 2026 and was last updated on August 18, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐧

🐧 Linux

Not in CISA KEV

HIGH severity

CVE-2026-74387

HIGH

CVE-2026-74387 is a high-severity (CVSS 7.8) vulnerability in Kernel. O3 Security confirms whether CVE-2026-74387 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

ALSA: seq: midi: Serialize output teardown with event_input

Published

Aug 15, 2026

Updated

Aug 18, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Aug 18, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🐧Kernel

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Linux packages — download data is not available via public APIs for these ecosystems.

Description

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

ALSA: seq: midi: Serialize output teardown with event_input

event_process_midi() borrows msynth->output_rfile.output and then passes the substream to dump_midi() and snd_rawmidi_kernel_write() without synchronizing with the output open/close transition. midisynth_use() also publishes output_rfile before snd_rawmidi_output_params() has finished.

The last midisynth_unuse() can therefore release the same rawmidi file and free substream->runtime before snd_rawmidi_kernel_write1() takes its runtime buffer reference. That leaves the event_input path using a stale substream or runtime and can end in a NULL-deref or use-after-free.

Fix this with two pieces of synchronization. Keep a short IRQ-safe spinlock only for publishing or clearing output_rfile and for pairing the output snapshot with an snd_use_lock_t reference. Once event_process_midi() has taken that in-flight reference, it drops the spinlock before calling snd_seq_dump_var_event(), dump_midi(), or snd_rawmidi_kernel_write(). midisynth_unuse() now detaches the visible rawmidi file under the same spinlock, waits for the in-flight writers to drain, and only then drains and releases the saved file. midisynth_use() likewise opens into a local snd_rawmidi_file and publishes it only after snd_rawmidi_output_params() succeeds.

The buggy scenario involves two paths, with each column showing the order within that path:

event_input path: last unuse path:

event_process_midi() snapshots 1. midisynth_unuse() starts output_rfile.output. tearing down output_rfile.
dump_midi() reaches 2. snd_rawmidi_kernel_release() snd_rawmidi_kernel_write() closes the output file. before runtime is pinned. 3. close_substream() frees
The callback keeps using substream->runtime. the borrowed substream.

Validation reproduced this kernel report: KASAN null-ptr-deref in snd_rawmidi_kernel_write1+0x56/0x360 RIP: 0033:0x7fde7dd0837f RIP: 0010:snd_rawmidi_kernel_write1+0x56/0x360

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐧Linux	`Kernel`	≥ 2.6.12&&< 6.1.178	6.1.178

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Kernel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Kernel to 6.1.178 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-74387 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-74387 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-74387. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

In the Linux kernel, the following vulnerability has been resolved: ALSA: seq: midi: Serialize output teardown with event_input event_process_midi() borrows msynth->output_rfile.output and then passes the substream to dump_midi() and snd_rawmidi_kernel_write() without synchronizing with the output open/close transition. midisynth_use() also publishes output_rfile before snd_rawmidi_output_params() has finished. The last midisynth_unuse() can therefore release the same rawmidi file and free substream->runtime before snd_rawmidi_kernel_write1() takes its runtime buffer reference. That leaves

O3 Security · Impact-Aware SCA

Is CVE-2026-74387 in your dependencies?

O3 detects CVE-2026-74387 across Linux dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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