{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-74503",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-74503"
  ],
  "published": "2026-08-15T12:28:42Z",
  "summary": "ALSA: timer: Clear SNDRV_TIMER_IFLG_DEAD once the close completes",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: timer: Clear SNDRV_TIMER_IFLG_DEAD once the close completes\n\nsnd_timer_close_locked() marks an instance with SNDRV_TIMER_IFLG_DEAD\nand returns early when the flag is already set, but the flag is never\ncleared again.  A completed close ends in remove_slave_links(), which\nleaves timeri->timer NULL, so a second close is already harmless through\nthe timer == NULL path; the early return can only be reached by an\ninstance that was opened again in between.  For such an instance the\nclose unlinks nothing, so snd_timer_instance_free() frees an object that\nis still on timer->open_list_head, still on snd_timer_master_list if it\nwas opened with a slave key, still owns any adopted slaves, and still\nholds its timer and module references.\n\nsnd_seq_timer_open() reopens an instance exactly like that: it retries\nits fallback open on the same object after a failure that has already\nrun snd_timer_close_locked() internally.  An unprivileged user with\naccess to /dev/snd/timer and /dev/snd/seq can force that failure, since\nsnd_timer_check_master() returns -EBUSY when a pending slave matches the\nnew master's (slave_class, slave_id) key and the target timer has\nreached max_instances, and SNDRV_TIMER_IOCTL_SELECT with dev_class =\nSNDRV_TIMER_CLASS_SLAVE keeps the caller-supplied dev_sclass, so a\nsequencer queue's key can be forged.  The freed instance is afterwards\ndereferenced by any further snd_timer_open() on that timer, by\nsnd_timer_check_slave(), and by /proc/asound/timers, which faults on the\nstale ti->owner pointer.\n\nThe flag only has to be visible while the close is in progress, which is\nall its other users need.  Clear it in remove_slave_links(), under the\nsame timer->lock that sets it, once the instance is off every list.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.12.96-1+rpt1"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.12.96+rpt-rpi-2712",
            "binary_version": "1:6.12.96-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.12.96+rpt-rpi-v6",
            "binary_version": "1:6.12.96-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.12.96+rpt-rpi-v7",
            "binary_version": "1:6.12.96-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.12.96+rpt-rpi-v7l",
            "binary_version": "1:6.12.96-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.12.96+rpt-rpi-v8",
            "binary_version": "1:6.12.96-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.12.96+rpt-rpi-v8-rt",
            "binary_version": "1:6.12.96-1+rpt1"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.12.96-1+rpt1": {
            "linux_commit": "ae161617d7a4552fa91d03626b8d9f3696d17481",
            "upstream_version": "6.12.96",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.12.103"
          }
        }
      }
    },
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:13",
        "name": "linux"
      },
      "versions": [
        "1:6.18.39-1+rpt1"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.18.39+rpt-rpi-2712",
            "binary_version": "1:6.18.39-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.18.39+rpt-rpi-v6",
            "binary_version": "1:6.18.39-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.18.39+rpt-rpi-v7",
            "binary_version": "1:6.18.39-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.18.39+rpt-rpi-v8",
            "binary_version": "1:6.18.39-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.18.39+rpt-rpi-v8-rt",
            "binary_version": "1:6.18.39-1+rpt1"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.18.39-1+rpt1": {
            "linux_commit": "60ea684a8ace97bb0db1a16e20753bdd6ab371ff",
            "upstream_version": "6.18.39",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.18.44"
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-74503"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/bb016091010ec401a06e6bdace0cd944ee03d371"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a26a2e52736f9e39843ca66a2e1ce6bf1adbcd1e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/0c561fab50991df10b1e4daca25886c34a2a9c07"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c2744d5f3aea474513fd2298daecb94a952ce441"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-17T05:50:24Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - Exploitation requires local ioctl access to /dev/snd/timer and /dev/snd/seq to forge timer slave keys and drive snd_seq_timer_open() retry logic; there is no network, adjacent-wireless, or physical-device entry path.\nAC:L - The attacker fully controls the ioctl and sequencer queue sequence that forces the initial -EBUSY close, retries snd_timer_open() on the same instance, and later triggers free; no uncontrollable timing, memory layout, or rare kernel state is required beyond standard ALSA being enabled.\nPR:L - The fix commit and reachable ioctl paths require only an unprivileged local user with access to ALSA device nodes (/dev/snd/timer and /dev/snd/seq), typical on desktops, kiosks, and Android systems via the audio group or equivalent permissions, not real root in the init namespace.\nUI:N - Exploitation is self-contained through attacker-initiated timer SELECT ioctls and sequencer queue open/close operations; no victim interaction such as opening files, mounting filesystems, or clicking prompts is required.\nS:U - Impact is kernel memory corruption and potential local privilege escalation within the same kernel address space; it does not cross a VM, container, or IOMMU security boundary into a separate authority.\nC:H - A use-after-free of snd_timer_instance leaves dangling list pointers; freed memory can be reallocated and later dereferenced by snd_timer_open(), snd_timer_check_slave(), or /proc/asound/timers, enabling arbitrary kernel memory read primitives.\nI:H - The UAF frees a structure still linked on timer open/master lists while retaining timer and module references, allowing heap reuse and memory corruption that can be leveraged for arbitrary kernel writes or control-flow hijacking.\nA:H - Stale timer instance pointers are dereferenced during subsequent timer operations and /proc/asound/timers reads, causing kernel faults/oops; UAF reliably threatens crashes even before full exploitation."
    }
  }
}