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CVE-2026-64029NVD status: Modified

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-64029 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 8ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb, 0cb1ad795570167558530d6194297ac2396a1991, 3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.1% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 8ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb or 0cb1ad795570167558530d6194297ac2396a1991 or 3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b or ef46b616a4c219185bbf10ebcbacb571583fd0e4, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.142 or 6.12.92 or 6.18.34 or 7.0.11, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux81fd444aa371261cd33f31d4ffd80faeeeab0cc9 up to, but not including, 8ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb; 81fd444aa371261cd33f31d4ffd80faeeeab0cc9 up to, but not including, 0cb1ad795570167558530d6194297ac2396a1991; 81fd444aa371261cd33f31d4ffd80faeeeab0cc9 up to, but not including, 3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b; 81fd444aa371261cd33f31d4ffd80faeeeab0cc9 up to, but not including, ef46b616a4c219185bbf10ebcbacb571583fd0e4; 81fd444aa371261cd33f31d4ffd80faeeeab0cc9 up to, but not including, 60a1969fae6209644698fca91c185d153674f631; 6.58ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb, 0cb1ad795570167558530d6194297ac2396a1991, 3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b, ef46b616a4c219185bbf10ebcbacb571583fd0e4, 60a1969fae6209644698fca91c185d153674f631
LinuxLinux Kernel6.5 up to, but not including, 6.6.142; 6.7 up to, but not including, 6.12.92; 6.13 up to, but not including, 6.18.34; 6.19 up to, but not including, 7.0.11; 7.16.6.142, 6.12.92, 6.18.34, 7.0.11

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: ALSA: seq: Serialize UMP output teardown with event_input seq_ump_process_event() borrows client->out_rfile.output without synchronizing with the first-open and last-close transition in seq_ump_client_open() and seq_ump_client_close(). The last output unuse can therefore drop opened[STR_OUT] to zero and release the rawmidi file while an in-flight event_input callback is still inside snd_rawmidi_kernel_write(). That leaves the rawmidi substream runtime exposed to teardown before the write path has taken its own buffer reference. Add a per-client rwlock for the event_input-visible output file. Publish a newly opened output file under the write side, and hold the read side from the output lookup through snd_rawmidi_kernel_write(). The last output close copies and clears the visible output file under the write side, then drops the lock and releases the saved rawmidi file. Use IRQ-safe rwlock guards because event_input can also be reached from atomic sequencer delivery. The buggy scenario involves two paths, with each column showing the order within that path: path A label: event_input path path B label: last unuse path 1. seq_ump_process_event() reads 1. seq_ump_client_close() client->out_rfile.output. drops opened[STR_OUT] to zero. 2. snd_rawmidi_kernel_write1() 2. snd_rawmidi_kernel_release() has not yet pinned runtime. closes the output file. 3. The writer continues using 3. close_substream() frees the borrowed substream. substream->runtime. This keeps the output substream and runtime alive for the full event_input write while keeping rawmidi release outside the rwlock. KASAN reproduced this as a slab-use-after-free in snd_rawmidi_kernel_write1(), with allocation through seq_ump_use()/snd_seq_port_connect() and free through seq_ump_unuse()/snd_seq_port_disconnect(). Validation reproduced this kernel report: KASAN slab-use-after-free in snd_rawmidi_kernel_write1+0x9d/0x400 RIP: 0033:0x7f5528af837f Read of size 8 Call trace: dump_stack_lvl+0x73/0xb0 (?:?) print_report+0xd1/0x650 (?:?) srso_alias_return_thunk+0x5/0xfbef5 (?:?) __virt_addr_valid+0x1a7/0x340 (?:?) kasan_complete_mode_report_info+0x64/0x200 (?:?) kasan_report+0xf7/0x130 (?:?) snd_rawmidi_kernel_write1+0x9d/0x400 (?:?) __asan_load8+0x82/0xb0 (?:?) update_stack_state+0x1ef/0x2d0 (?:?) snd_rawmidi_kernel_write+0x1a/0x20 (?:?) seq_ump_process_event+0xd4/0x120 (sound/core/seq/seq_ump_client.c:82) __snd_seq_deliver_single_event+0x8a/0xe0 (?:?) snd_seq_deliver_from_ump+0x2b2/0xd60 (?:?) lock_acquire+0x14e/0x2e0 (?:?) find_held_lock+0x31/0x90 (?:?) snd_seq_port_use_ptr+0xa6/0xe0 (?:?) __kasan_check_write+0x18/0x20 (?:?) do_raw_read_unlock+0x32/0xa0 (?:?) _raw_read_unlock+0x26/0x50 (?:?) snd_seq_deliver_single_event+0x45c/0x4b0 (?:?) snd_seq_deliver_event+0x10d/0x1b0 (?:?) snd_seq_client_enqueue_event+0x192/0x240 (?:?) snd_seq_write+0x2cd/0x450 (?:?) apparmor_file_permission+0x20/0x30 (?:?) security_file_permission+0x51/0x60 (?:?) vfs_write+0x1ce/0x850 (?:?) __fget_files+0x12b/0x220 (?:?) lock_release+0xc8/0x2a0 (?:?) __rcu_read_unlock+0x74/0x2d0 (?:?) __fget_files+0x135/0x220 (?:?) ksys_write+0x15a/0x180 (?:?) rcu_is_watching+0x24/0x60 (?:?) __x64_sys_write+0x46/0x60 (?:?) x64_sys_call+0x7d/0x20d0 (?:?) do_syscall_64+0xc1/0x360 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

How developers prevent this class of flaw

  • In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
  • Use thread-safe capabilities such as the data access abstraction in Spring.
  • Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

More Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities (CWE-362)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities

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