NULL Pointer Dereference Affecting kernel-debug-modules-core package, versions *
Threat Intelligence
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Test your applications- Snyk IDSNYK-CENTOS10-KERNELDEBUGMODULESCORE-19132221
- published21 Aug 2026
- disclosed15 Aug 2026
Introduced: 15 Aug 2026
NewCVE-2026-74387 (opens in a new tab)How to fix?
There is no fixed version for Centos:10 kernel-debug-modules-core.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-debug-modules-core package and not the kernel-debug-modules-core package as distributed by Centos.
See How to fix? for Centos:10 relevant fixed versions and status.
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
References
- https://bugzilla.redhat.com/show_bug.cgi?id=2516845
- https://access.redhat.com/security/cve/CVE-2026-74387
- https://git.kernel.org/stable/c/11165fe2c5ea0516debe486d91df67abbe36905e
- https://git.kernel.org/stable/c/718f6a56b40875f19e6915799044a02df9abfd52
- https://git.kernel.org/stable/c/936641af564c3d92721704b781e36aaf223efdd2
- https://git.kernel.org/stable/c/d6fd2afb137f52bf00c5210cc44d08ed54dcffb4
- https://git.kernel.org/stable/c/ef7607ab1c8adc6258fb1b27d08e26aecdc18a58
- https://git.kernel.org/stable/c/f5d470b808bc01f70978e22e595c6f7768313406