CVE-2026-64479 (GCVE-0-2026-64479)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:51 – Updated: 2026-08-17 04:56
VLAI
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 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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 6389f2c135311c4ce7c08c3b29145c8f95aacf1f , < d7649aa11089a93ea2285c210397aa67e5800766 (git)
Affected: d7e2ce72833bb23a82b4201fbed7214cc04a4a8c , < a224c84e5d3d35708c082c84ad12d81d90762195 (git)
Affected: 46397622a3fa8372b8fda0f04b33d16923b03b1b , < ea672a9f6cc38f06fe69dd2c257ef8a3d4db179a (git)
Affected: 46397622a3fa8372b8fda0f04b33d16923b03b1b , < fb1aa5082847b98f44f9c6272aee9d0dca9244f0 (git)
Affected: 46397622a3fa8372b8fda0f04b33d16923b03b1b , < 651ba82fe2a144bc7356d940bfd235c3810b0549 (git)
Affected: 46397622a3fa8372b8fda0f04b33d16923b03b1b , < 6ded42615fa1f4949925afd0a8a9e1ab3bf96202 (git)
Affected: 46397622a3fa8372b8fda0f04b33d16923b03b1b , < 435990e25bf1f4af3e6df12a6fbfd1f7ba4a97d4 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.5
Unaffected: 0 , < 6.5 (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.96 , ≤ 6.12.* (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: Fix uninitialised heap leak in snd_seq_event_dup()\n\nsnd_seq_event_dup() copies an incoming event into a pool cell and, in\nthe UMP-enabled build, clears the trailing cell-\u003eump.raw.extra word that\nthe memcpy() did not cover.  The guard deciding whether to clear it\ncompares the copied size against sizeof(cell-\u003eevent):\n\n\tmemcpy(\u0026cell-\u003eump, event, size);\n\tif (size \u003c sizeof(cell-\u003eevent))\n\t\tcell-\u003eump.raw.extra = 0;\n\nFor a legacy (non-UMP) event, size == sizeof(struct snd_seq_event) ==\nsizeof(cell-\u003eevent), so the condition is false and the extra word keeps\nstale data.  The cell pool is allocated with kvmalloc() (not zeroed) and\ncells are reused via a free list, so that word holds uninitialised heap\nor leftover event data.\n\nWhen such a cell is delivered to a UMP client (client-\u003emidi_version \u003e 0)\nthat set SNDRV_SEQ_FILTER_NO_CONVERT -- so the legacy event reaches it\nunconverted -- snd_seq_read() reads it out as the larger struct\nsnd_seq_ump_event and copies the stale word to user space, a 4-byte\nkernel heap infoleak to an unprivileged /dev/snd/seq client.\n\nCompare against sizeof(cell-\u003eump) instead, so the trailing word is zeroed\nfor every event shorter than the UMP cell."
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "dateReserved": "2026-07-19T15:36:31.791Z",
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: Fix uninitialised heap leak in snd_seq_event_dup()\n\nsnd_seq_event_dup() copies an incoming event into a pool cell and, in\nthe UMP-enabled build, clears the trailing cell-\u003eump.raw.extra word that\nthe memcpy() did not cover.  The guard deciding whether to clear it\ncompares the copied size against sizeof(cell-\u003eevent):\n\n\tmemcpy(\u0026cell-\u003eump, event, size);\n\tif (size \u003c sizeof(cell-\u003eevent))\n\t\tcell-\u003eump.raw.extra = 0;\n\nFor a legacy (non-UMP) event, size == sizeof(struct snd_seq_event) ==\nsizeof(cell-\u003eevent), so the condition is false and the extra word keeps\nstale data.  The cell pool is allocated with kvmalloc() (not zeroed) and\ncells are reused via a free list, so that word holds uninitialised heap\nor leftover event data.\n\nWhen such a cell is delivered to a UMP client (client-\u003emidi_version \u003e 0)\nthat set SNDRV_SEQ_FILTER_NO_CONVERT -- so the legacy event reaches it\nunconverted -- snd_seq_read() reads it out as the larger struct\nsnd_seq_ump_event and copies the stale word to user space, a 4-byte\nkernel heap infoleak to an unprivileged /dev/snd/seq client.\n\nCompare against sizeof(cell-\u003eump) instead, so the trailing word is zeroed\nfor every event shorter than the UMP cell."
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        "id": "CVE-2026-64479",
        "lastModified": "2026-08-17T05:17:53.653",
        "metrics": {},
        "published": "2026-07-25T10:17:33.493",
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      "cve": "CVE-2026-64479",
      "id": "CVE-2026-64479",
      "initial_release_date": "2026-07-25T00:00:00+00:00",
      "product_status:known_affected": "198",
      "product_status:known_not_affected": "76",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ALSA: seq: Fix uninitialised heap leak in snd_seq_event_dup()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64479.json",
      "version": "3"
    },
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      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-18T00:39:40Z",
      "cve": "CVE-2026-64479",
      "id": "CVE-2026-64479",
      "initial_release_date": "2026-07-25T15:58:34Z",
      "product_status:known_affected": "424",
      "product_status:known_not_affected": "309",
      "product_status:recommended": "111",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64479",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64479.json",
      "version": "10"
    }
  }
}



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