{"id":"CVE-2026-74387","title":"ALSA: seq: midi: Serialize output teardown with event_input","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: midi: Serialize output teardown with event_input\n\nevent_process_midi() borrows msynth->output_rfile.output and then\npasses the substream to dump_midi() and s…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < f5d470b808bc01f70978e22e595c6f7768313406","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 936641af564c3d92721704b781e36aaf223efdd2","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 718f6a56b40875f19e6915799044a02df9abfd52","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 11165fe2c5ea0516debe486d91df67abbe36905e","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < d6fd2afb137f52bf00c5210cc44d08ed54dcffb4","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ef7607ab1c8adc6258fb1b27d08e26aecdc18a58","Linux 2.6.12"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T18:55:07.666798Z"},"published":"2026-08-15","updated":"2026-10-16","sourceUpdated":"2026-10-16T18:55:36.992Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-74387","references":[{"url":"https://git.kernel.org/stable/c/f5d470b808bc01f70978e22e595c6f7768313406"},{"url":"https://git.kernel.org/stable/c/936641af564c3d92721704b781e36aaf223efdd2"},{"url":"https://git.kernel.org/stable/c/718f6a56b40875f19e6915799044a02df9abfd52"},{"url":"https://git.kernel.org/stable/c/11165fe2c5ea0516debe486d91df67abbe36905e"},{"url":"https://git.kernel.org/stable/c/d6fd2afb137f52bf00c5210cc44d08ed54dcffb4"},{"url":"https://git.kernel.org/stable/c/ef7607ab1c8adc6258fb1b27d08e26aecdc18a58"}],"tags":["cve.org"],"epss":0.00171,"epssPercentile":0.06041,"ingestedAt":"2026-10-16T19:46:24.372Z","slug":"CVE-2026-74387","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: midi: Serialize output teardown with event_input\n\nevent_process_midi() borrows msynth->output_rfile.output and then\npasses the substream to dump_midi() and snd_rawmidi_kernel_write()\nwithout synchronizing with the output open/close transition.\nmidisynth_use() also publishes output_rfile before\nsnd_rawmidi_output_params() has finished.\n\nThe last midisynth_unuse() can therefore release the same rawmidi file\nand free substream->runtime before snd_rawmidi_kernel_write1() takes\nits runtime buffer reference. That leaves the event_input path using a\nstale substream or runtime and can end in a NULL-deref or use-after-free.\n\nFix this with two pieces of synchronization. Keep a short IRQ-safe\nspinlock only for publishing or clearing output_rfile and for pairing\nthe output snapshot with an snd_use_lock_t reference. Once\nevent_process_midi() has taken that in-flight reference, it drops the\nspinlock before calling snd_seq_dump_var_event(), dump_midi(), or\nsnd_rawmidi_kernel_write(). midisynth_unuse() now detaches the visible\nrawmidi file under the same spinlock, waits for the in-flight writers\nto drain, and only then drains and releases the saved file.\nmidisynth_use() likewise opens into a local snd_rawmidi_file and\npublishes it only after snd_rawmidi_output_params() succeeds.\n\nThe buggy scenario involves two paths, with each column showing the\norder within that path:\n\nevent_input path:                     last unuse path:\n1. event_process_midi() snapshots    1. midisynth_unuse() starts\n   output_rfile.output.                 tearing down output_rfile.\n2. dump_midi() reaches               2. snd_rawmidi_kernel_release()\n   snd_rawmidi_kernel_write()           closes the output file.\n   before runtime is pinned.         3. close_substream() frees\n3. The callback keeps using             substream->runtime.\n   the borrowed substream.\n\nValidation reproduced this kernel report:\nKASAN null-ptr-deref in snd_rawmidi_kernel_write1+0x56/0x360\nRIP: 0033:0x7fde7dd0837f\nRIP: 0010:snd_rawmidi_kernel_write1+0x56/0x360\n\n## Affected\n\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < f5d470b808bc01f70978e22e595c6f7768313406`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 936641af564c3d92721704b781e36aaf223efdd2`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 718f6a56b40875f19e6915799044a02df9abfd52`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 11165fe2c5ea0516debe486d91df67abbe36905e`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < d6fd2afb137f52bf00c5210cc44d08ed54dcffb4`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ef7607ab1c8adc6258fb1b27d08e26aecdc18a58`\n- `Linux 2.6.12`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}