CVE-2026-74278
Received Received - Intake

Heap Address Leak in Linux Kernel ALSA Sequencer

Publication date: 2026-08-15

Last updated on: 2026-08-15

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ALSA: seq: Fix kernel heap address leak in bounce_error_event() The comment above bounce_error_event() documents that user clients should receive SNDRV_SEQ_EVENT_BOUNCE with the original event embedded as variable-length data, while kernel clients should receive SNDRV_SEQ_EVENT_KERNEL_ERROR with a quoted kernel pointer. However, the implementation unconditionally uses SNDRV_SEQ_EVENT_KERNEL_ERROR with data.quote.event set to the raw struct snd_seq_event pointer for all clients. When a bounce error event is delivered to a USER_CLIENT via snd_seq_read(), the kernel heap address in data.quote.event is exposed to userspace through copy_to_user() in the fixed-length branch. This is a distinct leak path from the one addressed by commit 705dd6dcbc0e ("ALSA: seq: Clear variable event pointer on read"), which sanitizes data.ext.ptr in the variable-length branch of snd_seq_read(). The bounce_error_event() leak uses fixed-length events that take the else branch where no sanitization occurs. Differentiate the bounce event by client type. For USER_CLIENT, send SNDRV_SEQ_EVENT_BOUNCE with SNDRV_SEQ_EVENT_LENGTH_VARIABLE and data.ext pointing to the original event. The variable-length path in snd_seq_event_dup() copies the event data into chained cells, and snd_seq_expand_var_event() copies only the content -- never the pointer -- to userspace. For KERNEL_CLIENT, keep the existing SNDRV_SEQ_EVENT_KERNEL_ERROR behavior with the quoted pointer.

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Meta Information

Published
2026-08-15
Last Modified
2026-08-15
Generated
2026-08-15
AI Q&A
2026-08-15
EPSS Evaluated
N/A
NVD
CVE-2026-74278
EUVD
EUVD-2026-59425

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a kernel heap address leak in the Linux ALSA sequencer subsystem. The function bounce_error_event() incorrectly sends kernel pointers to userspace clients via SNDRV_SEQ_EVENT_KERNEL_ERROR, exposing heap memory addresses through copy_to_user(). The fix differentiates event handling based on client type to prevent this leak.

Detection Guidance

This vulnerability involves a kernel heap address leak in the ALSA sequencer subsystem. Detection requires checking for unpatched Linux kernels and examining ALSA sequencer event handling logs. No direct network detection commands are provided in the context.

Impact Analysis

An attacker with local access could exploit this to leak kernel heap memory addresses. This information could aid in bypassing kernel security mechanisms or facilitate further exploits targeting kernel memory corruption vulnerabilities.

Mitigation Strategies

Apply the kernel patch that fixes the bounce_error_event() implementation. Update to a Linux kernel version that includes the fix for CVE-2026-74278. Monitor ALSA sequencer subsystem logs for suspicious events.

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