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GHSA-5RP2-CP2V-9MCX

Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-15 06:32
VLAI
Details

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

ALSA: seq: Clear variable event pointer on read

snd_seq_read() copies a queued variable-length event header to userspace before expanding the payload. Queued variable-length events use SNDRV_SEQ_EXT_CHAINED internally, and data.ext.ptr points at the first extension cell.

The read side strips SNDRV_SEQ_EXT_* bits from data.ext.len before the copy, but it leaves data.ext.ptr untouched. A userspace sequencer client can therefore write a direct variable event to itself and read back the extension-cell kernel address from the returned header.

Clear the temporary header pointer before copy_to_user(). The original queued event remains unchanged and is still passed to snd_seq_expand_var_event(), so payload expansion keeps using the internal chain.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-74339"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-15T06:22:34Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: Clear variable event pointer on read\n\nsnd_seq_read() copies a queued variable-length event header to userspace\nbefore expanding the payload. Queued variable-length events use\nSNDRV_SEQ_EXT_CHAINED internally, and data.ext.ptr points at the first\nextension cell.\n\nThe read side strips SNDRV_SEQ_EXT_* bits from data.ext.len before the\ncopy, but it leaves data.ext.ptr untouched. A userspace sequencer client\ncan therefore write a direct variable event to itself and read back the\nextension-cell kernel address from the returned header.\n\nClear the temporary header pointer before copy_to_user(). The original\nqueued event remains unchanged and is still passed to\nsnd_seq_expand_var_event(), so payload expansion keeps using the\ninternal chain.",
  "id": "GHSA-5rp2-cp2v-9mcx",
  "modified": "2026-08-15T06:32:30Z",
  "published": "2026-08-15T06:32:30Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74339"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/14fe4f75fd5309d6b75f8e840ada88912b374207"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6b52211eba213c461f68922708a99d8190c1fcd5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/705dd6dcbc0ea87351c660c1a6443f85f1001c76"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/74ac1ce1f4afdb3b80b6742fa28fb86c8c51d31b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c2ac9287e89916da684c2a548798351e63eb59ee"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e0c3edd86414534cfd179fefe45b38c29c01ae7a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f29243c211928114f8b906e0a3fee77c236f14c8"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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