CVE-2026-64029 - Vulnerability Details

- ALSA: seq: Serialize UMP output teardown with event_input

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 (?:?)

Published: 2026-07-19

Score: 7.8 High

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

A race condition in the Linux kernel ALSA sequencer allows the rawmidi substream runtime to be freed while a write callback is still executing, resulting in a use‑after‑free that can crash the kernel. This flaw is triggered when an event_input is processed concurrently with the teardown of the output file, exposing the kernel to a denial of service. The vulnerability is identified as a classic use‑after‑free (CWE‑362, CWE‑364).

Affected Systems

All Linux kernel builds that include the ALSA sequencer module before the fix that added a per‑client rwlock are affected. Vendors are represented by the Linux operating system, and product versions range across all kernel releases except those after the commit series that addressed the issue (e.g., kernel 7.1 and later releases with the patch). The supplied CPE strings indicate all Linux kernel variants, including the 7.1 release candidates.

Risk and Exploitability

The CVSS score of 7.8 indicates a high severity issue, while the EPSS score of less than 1% and the absence from the CISA KEV catalog suggest a low likelihood of current exploitation. An attacker would need to trigger an ALSA event_input while simultaneously closing an output file, a scenario described in the vulnerability details. The flaw leads to a use‑after‑free that can crash the kernel and result in a denial of service if successfully exploited. The description does not outline the privilege level required to carry out the actions.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`81fd444aa371261cd33f31d4ffd80faeeeab0cc9`	affected	< 8ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb
`81fd444aa371261cd33f31d4ffd80faeeeab0cc9`	affected	< 0cb1ad795570167558530d6194297ac2396a1991
`81fd444aa371261cd33f31d4ffd80faeeeab0cc9`	affected	< 3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b
`81fd444aa371261cd33f31d4ffd80faeeeab0cc9`	affected	< ef46b616a4c219185bbf10ebcbacb571583fd0e4
`81fd444aa371261cd33f31d4ffd80faeeeab0cc9`	affected	< 60a1969fae6209644698fca91c185d153674f631

Linux

affected

Version	Status	Constraints
`6.5`	affected	—
`0`	unaffected	< 6.5
`6.6.142`	unaffected	≤ 6.6.*
`6.12.92`	unaffected	≤ 6.12.*
`6.18.34`	unaffected	≤ 6.18.*
`7.0.11`	unaffected	≤ 7.0.*
`7.1`	unaffected	≤ *

Configuration 1 [-]

OR	cpe:2.3:o:linux:linux_kernel::::::::
	cpe:2.3:o:linux:linux_kernel::::::::
	cpe:2.3:o:linux:linux_kernel::::::::
	cpe:2.3:o:linux:linux_kernel::::::::
	cpe:2.3:o:linux:linux_kernel:7.1:rc1::::::
	cpe:2.3:o:linux:linux_kernel:7.1:rc2::::::
	cpe:2.3:o:linux:linux_kernel:7.1:rc3::::::
	cpe:2.3:o:linux:linux_kernel:7.1:rc4::::::

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[81fd444aa371261cd33f31d4ffd80faeeeab0cc9,8ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb)`	affected	code_commit	—
`[81fd444aa371261cd33f31d4ffd80faeeeab0cc9,0cb1ad795570167558530d6194297ac2396a1991)`	affected	code_commit	—
`[81fd444aa371261cd33f31d4ffd80faeeeab0cc9,3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b)`	affected	code_commit	—
`[81fd444aa371261cd33f31d4ffd80faeeeab0cc9,ef46b616a4c219185bbf10ebcbacb571583fd0e4)`	affected	code_commit	—
`[81fd444aa371261cd33f31d4ffd80faeeeab0cc9,60a1969fae6209644698fca91c185d153674f631)`	affected	code_commit	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`6.5`	affected	generic	—
`[0,6.5)`	unaffected	generic	—
`[6.6.142,6.7.0)`	unaffected	semver	—
`[6.12.92,6.13.0)`	unaffected	semver	—
`[6.18.34,6.19.0)`	unaffected	semver	—
`[7.0.11,7.1.0)`	unaffected	semver	—
`[7.1,*]`	unaffected	generic	—

Found an issue or want to improve our Enrichment? You can suggest it directly by opening an issue on our dedicated GitHub repository .

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Update the kernel to a version that includes the patch adding a per‑client read/write lock for the event_input‑visible output file (commits after 0cb1ad7).
If a kernel upgrade is not immediately possible, disable or unload the ALSA sequencer module on systems that do not require it, or restrict access to ALSA sequencer services for untrusted processes.
Continuously monitor system logs for KASAN or BUG reports mentioning ‘use‑after‑free’ in snd_rawmidi_kernel_write1 to detect and respond to potential crashes before they cause a denial of service.

Generated by OpenCVE AI on October 17, 2026 at 10:51 UTC.

Tracking

Sign in to view the affected projects.

Advisories

Source	ID	Title
Ubuntu USN	USN-8593-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8603-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-8618-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8663-1	Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN	USN-8664-1	Linux kernel (NVIDIA BaseOS) vulnerabilities
Ubuntu USN	USN-8728-1	Linux kernel (GCP) vulnerabilities
Ubuntu USN	USN-8729-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8761-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-8729-2	Linux kernel (Raspberry Pi Real-time) vulnerabilities
Ubuntu USN	USN-8761-2	Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN	USN-8781-1	Linux kernel (NVIDIA Tegra) vulnerabilities
Ubuntu USN	USN-8729-3	Linux kernel vulnerabilities
Ubuntu USN	USN-8802-1	Linux kernel (Oracle) vulnerabilities
Ubuntu USN	USN-8728-2	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-8729-4	Linux kernel (Low Latency) vulnerabilities
Ubuntu USN	USN-8729-5	Linux kernel (AWS FIPS) vulnerabilities
Ubuntu USN	USN-8728-3	Linux kernel (Oracle) vulnerabilities
Ubuntu USN	USN-8729-6	Linux kernel (AWS) vulnerabilities
Ubuntu USN	USN-8906-1	Linux kernel (IBM) vulnerabilities

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00097.

Exploitation none

Automatable no

Technical Impact total

References

Link	Providers
https://git.kernel.org/stable/c/0cb1ad795570167558530d6194297ac2396a1991
https://git.kernel.org/stable/c/3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b
https://git.kernel.org/stable/c/60a1969fae6209644698fca91c185d153674f631
https://git.kernel.org/stable/c/8ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb
https://git.kernel.org/stable/c/ef46b616a4c219185bbf10ebcbacb571583fd0e4
https://lore.kernel.org/linux-cve-announce/2026071903-CVE-2026-64029-4b58@gregkh/T
https://nvd.nist.gov/vuln/detail/CVE-2026-64029
https://www.cve.org/CVERecord?id=CVE-2026-64029

History

Fri, 16 Oct 2026 17:30:00 +0000

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}`

Tue, 13 Oct 2026 15:45:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-362
CPEs		cpe:2.3:o:linux:linux_kernel:7.1:rc1:::::: cpe:2.3:o:linux:linux_kernel:7.1:rc2:::::: cpe:2.3:o:linux:linux_kernel:7.1:rc3:::::: cpe:2.3:o:linux:linux_kernel:7.1:rc4::::::

Wed, 22 Jul 2026 12:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-364
References		https://lore.kernel.org/linux-cve-announce/2026071903-CVE-2026-64029-4b58@gregkh/T https://nvd.nist.gov/vuln/detail/CVE-2026-64029 https://www.cve.org/CVERecord?id=CVE-2026-64029
Metrics	threat_severity `None`	threat_severity `Moderate`

Mon, 20 Jul 2026 14:45:00 +0000

Type	Values Removed	Values Added
Metrics		cvssV3_1 `{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}`

Sun, 19 Jul 2026 15:45:00 +0000

Type	Values Removed	Values Added
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 (?:?)
Title		ALSA: seq: Serialize UMP output teardown with event_input
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/0cb1ad795570167558530d6194297ac2396a1991 https://git.kernel.org/stable/c/3aab4a58d23fb22dac5b558bbe5df1a8dad00b4b https://git.kernel.org/stable/c/60a1969fae6209644698fca91c185d153674f631 https://git.kernel.org/stable/c/8ba1c4ddbb1c67d34bb440aecb9f5690ed3f64cb https://git.kernel.org/stable/c/ef46b616a4c219185bbf10ebcbacb571583fd0e4

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-07-19T15:39:20.368Z

Updated: 2026-10-19T20:28:09.426Z

Reserved: 2026-07-19T07:54:57.028Z

Link: CVE-2026-64029

Vulnrichment

Updated: 2026-10-16T15:35:35.392Z

NVD

Status : Modified

Published: 2026-07-19T16:17:42.997

Modified: 2026-10-19T21:17:20.393

Link: CVE-2026-64029

Redhat

Severity : Moderate

Publid Date: 2026-07-19T00:00:00Z

Links: CVE-2026-64029 - Bugzilla

OpenCVE Enrichment

Updated: 2026-10-17T11:00:07Z

Weaknesses

CWE-362
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CWE-364
Signal Handler Race Condition

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

Exploitation none

Automatable no

Technical Impact total

Subscriptions

JSON object

JSON object

JSON object

JSON object

JSON object