GHSA-5CW4-RFP6-XJFX

Vulnerability from github – Published: 2026-05-08 15:31 – Updated: 2026-05-21 18:33
VLAI
Details

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

ALSA: pcm: fix use-after-free on linked stream runtime in snd_pcm_drain()

In the drain loop, the local variable 'runtime' is reassigned to a linked stream's runtime (runtime = s->runtime at line 2157). After releasing the stream lock at line 2169, the code accesses runtime->no_period_wakeup, runtime->rate, and runtime->buffer_size (lines 2170-2178) — all referencing the linked stream's runtime without any lock or refcount protecting its lifetime.

A concurrent close() on the linked stream's fd triggers snd_pcm_release_substream() → snd_pcm_drop() → pcm_release_private() → snd_pcm_unlink() → snd_pcm_detach_substream() → kfree(runtime). No synchronization prevents kfree(runtime) from completing while the drain path dereferences the stale pointer.

Fix by caching the needed runtime fields (no_period_wakeup, rate, buffer_size) into local variables while still holding the stream lock, and using the cached values after the lock is released.

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-43437"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-08T15:16:56Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: pcm: fix use-after-free on linked stream runtime in snd_pcm_drain()\n\nIn the drain loop, the local variable \u0027runtime\u0027 is reassigned to a\nlinked stream\u0027s runtime (runtime = s-\u003eruntime at line 2157).  After\nreleasing the stream lock at line 2169, the code accesses\nruntime-\u003eno_period_wakeup, runtime-\u003erate, and runtime-\u003ebuffer_size\n(lines 2170-2178) \u2014 all referencing the linked stream\u0027s runtime without\nany lock or refcount protecting its lifetime.\n\nA concurrent close() on the linked stream\u0027s fd triggers\nsnd_pcm_release_substream() \u2192 snd_pcm_drop() \u2192 pcm_release_private()\n\u2192 snd_pcm_unlink() \u2192 snd_pcm_detach_substream() \u2192 kfree(runtime).\nNo synchronization prevents kfree(runtime) from completing while the\ndrain path dereferences the stale pointer.\n\nFix by caching the needed runtime fields (no_period_wakeup, rate,\nbuffer_size) into local variables while still holding the stream lock,\nand using the cached values after the lock is released.",
  "id": "GHSA-5cw4-rfp6-xjfx",
  "modified": "2026-05-21T18:33:06Z",
  "published": "2026-05-08T15:31:28Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-43437"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4a758e9a1f5ed722f83c4dd35f867fe811553bcb"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/629cf09464cf98670996ea5c191dc9743e6f3f00"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9b1dbd69ba6f8f8c69bc7b77c2ce3b9c6ed05ba6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9baee36e8c5443411c4629afabafaff8a46a23fd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ae8f8d30d334bad5b1b3cdb1eb8a0b771f55e432"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c2f64e05a0587a83ec42dbd6b7a7ded79b2ff694"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fc71f888994569f87d5bee20b1ac6c9c1e3a7a79"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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