GHSA-JG2J-FXRH-W676

Vulnerability from github – Published: 2026-10-18 18:32 – Updated: 2026-10-30 15:33
VLAI
Details

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

Bluetooth: RFCOMM: Fix initial port reference race

For RFCOMM_RELEASE_ONHUP devices, rfcomm_tty_install() and __rfcomm_release_dev() both use RFCOMM_TTY_OWNED to decide who drops the initial tty_port reference. The release path tests the bit separately from the install path setting it, so both can drop that reference.

The synchronous hangup does not prevent this race: port->tty is not assigned until tty_port_open(), after installation. The following interleaving is possible:

  1. Install and release each obtain a reference with rfcomm_dev_get().
  2. Release observes RFCOMM_TTY_OWNED clear.
  3. Install sets RFCOMM_TTY_OWNED and drops the initial reference.
  4. Release drops the same initial reference again.
  5. TTY cleanup drops its reference and frees the device.
  6. Release performs its final tty_port_put() on the freed port.

KASAN reported:

BUG: KASAN: slab-use-after-free in tty_port_put+0x22/0x190 Write of size 4 at addr ffff8881001d3d5c by task poc/92

Call Trace: tty_port_put+0x22/0x190 rfcomm_dev_ioctl+0x1d4/0x1930 sock_do_ioctl+0x110/0x260 sock_ioctl+0x380/0x590 __x64_sys_ioctl+0x134/0x1c0

Allocated by task 88: rfcomm_dev_ioctl+0x8f6/0x1930 sock_do_ioctl+0x110/0x260 sock_ioctl+0x380/0x590 __x64_sys_ioctl+0x134/0x1c0

Freed by task 65: kfree+0x131/0x3c0 rfcomm_dev_destruct+0x23b/0x2f0 release_one_tty+0xc1/0x370 process_one_work+0x661/0x1090

Use test_and_set_bit() in both paths so that only the caller that changes RFCOMM_TTY_OWNED from clear to set drops the initial reference. Each path keeps its own lookup reference until release or TTY cleanup, preserving the existing callback ordering and error handling.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98739"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-18T16:17:27Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: RFCOMM: Fix initial port reference race\n\nFor RFCOMM_RELEASE_ONHUP devices, rfcomm_tty_install() and\n__rfcomm_release_dev() both use RFCOMM_TTY_OWNED to decide who drops the\ninitial tty_port reference. The release path tests the bit separately\nfrom the install path setting it, so both can drop that reference.\n\nThe synchronous hangup does not prevent this race: port-\u003etty is not\nassigned until tty_port_open(), after installation. The following\ninterleaving is possible:\n\n  1. Install and release each obtain a reference with rfcomm_dev_get().\n  2. Release observes RFCOMM_TTY_OWNED clear.\n  3. Install sets RFCOMM_TTY_OWNED and drops the initial reference.\n  4. Release drops the same initial reference again.\n  5. TTY cleanup drops its reference and frees the device.\n  6. Release performs its final tty_port_put() on the freed port.\n\nKASAN reported:\n\n  BUG: KASAN: slab-use-after-free in tty_port_put+0x22/0x190\n  Write of size 4 at addr ffff8881001d3d5c by task poc/92\n\n  Call Trace:\n   tty_port_put+0x22/0x190\n   rfcomm_dev_ioctl+0x1d4/0x1930\n   sock_do_ioctl+0x110/0x260\n   sock_ioctl+0x380/0x590\n   __x64_sys_ioctl+0x134/0x1c0\n\n  Allocated by task 88:\n   rfcomm_dev_ioctl+0x8f6/0x1930\n   sock_do_ioctl+0x110/0x260\n   sock_ioctl+0x380/0x590\n   __x64_sys_ioctl+0x134/0x1c0\n\n  Freed by task 65:\n   kfree+0x131/0x3c0\n   rfcomm_dev_destruct+0x23b/0x2f0\n   release_one_tty+0xc1/0x370\n   process_one_work+0x661/0x1090\n\nUse test_and_set_bit() in both paths so that only the caller that changes\nRFCOMM_TTY_OWNED from clear to set drops the initial reference. Each path\nkeeps its own lookup reference until release or TTY cleanup, preserving\nthe existing callback ordering and error handling.",
  "id": "GHSA-jg2j-fxrh-w676",
  "modified": "2026-10-30T15:33:58Z",
  "published": "2026-10-18T18:32:01Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98739"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0a554901bd227537f79220443b2b36d585d62893"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2d696c1ed3468dcb62578a3911e687110d463520"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/55d162aa00d1ee33c3e6fa88b71f1e2d6e1441e9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a03ccf1ab77380d4c4a3c56552e12de4a83efa21"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c50360a019766fafa27318928bfea96dcce8a37d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cd247e38b14df48d6b3940c4573a9f7acb10c363"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d3dd18e85c140df72e0f2b5ee156ebfba04c06cb"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e5aa7fbf7a4446bb89f0b8394b2dfc1a6b6aba5b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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