---
id: CVE-2026-64479
title: 'ALSA: seq: Fix uninitialised heap leak in snd_seq_event_dup()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ALSA: seq: Fix uninitialised heap leak in snd_seq_event_dup()

  snd_seq_event_dup() copies an incoming event into a pool cell and, in
  the UMP-enabled build, clears the t…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 6389f2c135311c4ce7c08c3b29145c8f95aacf1f <
    d7649aa11089a93ea2285c210397aa67e5800766
  - >-
    Linux >= d7e2ce72833bb23a82b4201fbed7214cc04a4a8c <
    a224c84e5d3d35708c082c84ad12d81d90762195
  - >-
    Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b <
    ea672a9f6cc38f06fe69dd2c257ef8a3d4db179a
  - >-
    Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b <
    fb1aa5082847b98f44f9c6272aee9d0dca9244f0
  - >-
    Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b <
    651ba82fe2a144bc7356d940bfd235c3810b0549
  - >-
    Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b <
    6ded42615fa1f4949925afd0a8a9e1ab3bf96202
  - >-
    Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b <
    435990e25bf1f4af3e6df12a6fbfd1f7ba4a97d4
  - Linux 6.5
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T16:39:55.990458Z'
published: '2026-07-25'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T16:44:54.844Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-64479'
references:
  - url: 'https://git.kernel.org/stable/c/d7649aa11089a93ea2285c210397aa67e5800766'
  - url: 'https://git.kernel.org/stable/c/a224c84e5d3d35708c082c84ad12d81d90762195'
  - url: 'https://git.kernel.org/stable/c/ea672a9f6cc38f06fe69dd2c257ef8a3d4db179a'
  - url: 'https://git.kernel.org/stable/c/fb1aa5082847b98f44f9c6272aee9d0dca9244f0'
  - url: 'https://git.kernel.org/stable/c/651ba82fe2a144bc7356d940bfd235c3810b0549'
  - url: 'https://git.kernel.org/stable/c/6ded42615fa1f4949925afd0a8a9e1ab3bf96202'
  - url: 'https://git.kernel.org/stable/c/435990e25bf1f4af3e6df12a6fbfd1f7ba4a97d4'
tags:
  - cve.org
epss: 0.00181
epssPercentile: 0.07708
ingestedAt: '2026-11-06T16:57:43.164Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

ALSA: seq: Fix uninitialised heap leak in snd_seq_event_dup()

snd_seq_event_dup() copies an incoming event into a pool cell and, in
the UMP-enabled build, clears the trailing cell->ump.raw.extra word that
the memcpy() did not cover.  The guard deciding whether to clear it
compares the copied size against sizeof(cell->event):

	memcpy(&cell->ump, event, size);
	if (size < sizeof(cell->event))
		cell->ump.raw.extra = 0;

For a legacy (non-UMP) event, size == sizeof(struct snd_seq_event) ==
sizeof(cell->event), so the condition is false and the extra word keeps
stale data.  The cell pool is allocated with kvmalloc() (not zeroed) and
cells are reused via a free list, so that word holds uninitialised heap
or leftover event data.

When such a cell is delivered to a UMP client (client->midi_version > 0)
that set SNDRV_SEQ_FILTER_NO_CONVERT -- so the legacy event reaches it
unconverted -- snd_seq_read() reads it out as the larger struct
snd_seq_ump_event and copies the stale word to user space, a 4-byte
kernel heap infoleak to an unprivileged /dev/snd/seq client.

Compare against sizeof(cell->ump) instead, so the trailing word is zeroed
for every event shorter than the UMP cell.

## Affected

- `Linux >= 6389f2c135311c4ce7c08c3b29145c8f95aacf1f < d7649aa11089a93ea2285c210397aa67e5800766`
- `Linux >= d7e2ce72833bb23a82b4201fbed7214cc04a4a8c < a224c84e5d3d35708c082c84ad12d81d90762195`
- `Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b < ea672a9f6cc38f06fe69dd2c257ef8a3d4db179a`
- `Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b < fb1aa5082847b98f44f9c6272aee9d0dca9244f0`
- `Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b < 651ba82fe2a144bc7356d940bfd235c3810b0549`
- `Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b < 6ded42615fa1f4949925afd0a8a9e1ab3bf96202`
- `Linux >= 46397622a3fa8372b8fda0f04b33d16923b03b1b < 435990e25bf1f4af3e6df12a6fbfd1f7ba4a97d4`
- `Linux 6.5`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.