{
  "cveId": "CVE-2026-99203",
  "url": "https://patchblox.com/security/cve/CVE-2026-99203",
  "summary": "CVE-2026-99203 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-99203, released November 3, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "pipe: preserve existing fasync readers on writer setup failure",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  pipe: preserve existing fasync readers on writer setup failure  F_SETFL and FIOASYNC decide whether to invoke -\u003Efasync() before pipe_fasync() takes pipe-\u003Emutex. Two enables of one O_RDWR FIFO can therefore both enter the callback.  fasync_helper() allocates before checking for an existing entry. If the first enable installs both entries, a second enable can update the reader entry and then fail the allocation for the writer entry. The error path removes the pre-existing reader entry, clearing FASYNC while the writer entry remains registered. __fput() then skips -\u003Efasync(), so a later pipe notification can dereference the freed file or its f_owner. An unprivileged memory-pressure reproducer triggers a KASAN slab-use-after-free in send_sigio() through this path.  Keep the reader helper\u0027s result and undo the registration only if this call added it. The pipe mutex serializes changes to both lists, so a failed new registration still removes its reader, while a failed duplicate preserves the existing registrations and FASYNC. Successful duplicate enables continue to update fa_fd as before.",
  "published": "2026-10-28T11:17:41Z",
  "severity": "Moderate",
  "cvss": 7.8,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
  "epss": 0.00121,
  "epssPercentile": 0.01946,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-99203",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.115-2",
      "fix": "DEBIAN-CVE-2026-99203",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-99203",
      "released": "2026-11-03T18:58:21Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.2.13-1",
      "fix": "DEBIAN-CVE-2026-99203",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-99203",
      "released": "2026-11-03T18:58:21Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T13:06:02Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}