CVE-2026-99203

Full vulnerability record from the local CVENow database.

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 ->fasync() before pipe_fasync() takes pipe->mutex. 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 ->fasync(), 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's 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.

Severity

Not scored

CVSS score

Not available

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-10-28 11:17:41.517000

Last modified

2026-10-28 11:17:41.517000

View original CVE JSON

{
  "id": "CVE-2026-99203",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-10-28T11:17:41.517",
  "lastModified": "2026-10-28T11:17:41.517",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npipe: preserve existing fasync readers on writer setup failure\n\nF_SETFL and FIOASYNC decide whether to invoke ->fasync() before\npipe_fasync() takes pipe->mutex. Two enables of one O_RDWR FIFO can\ntherefore both enter the callback.\n\nfasync_helper() allocates before checking for an existing entry. If the\nfirst enable installs both entries, a second enable can update the\nreader entry and then fail the allocation for the writer entry. The\nerror path removes the pre-existing reader entry, clearing FASYNC while\nthe writer entry remains registered. __fput() then skips ->fasync(), so a\nlater pipe notification can dereference the freed file or its f_owner.\nAn unprivileged memory-pressure reproducer triggers a KASAN\nslab-use-after-free in send_sigio() through this path.\n\nKeep the reader helper's result and undo the registration only if this\ncall added it. The pipe mutex serializes changes to both lists, so a\nfailed new registration still removes its reader, while a failed\nduplicate preserves the existing registrations and FASYNC. Successful\nduplicate enables continue to update fa_fd as before."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/pipe.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "76398425bb06b07cc3a3b1ce169c67dc9d6874ed",
              "lessThan": "4c42ce499ce4b1c787e61082e3b13df4f30c4eaa",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "76398425bb06b07cc3a3b1ce169c67dc9d6874ed",
              "lessThan": "2259809e5b7043c4ba20af7b14ba3e471cf55521",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "76398425bb06b07cc3a3b1ce169c67dc9d6874ed",
              "lessThan": "40bb03d3ea6f6a915218508819ecc4d7a7fa260d",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/pipe.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "2.6.30",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "2.6.30",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.59",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.13",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {},
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/2259809e5b7043c4ba20af7b14ba3e471cf55521",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/40bb03d3ea6f6a915218508819ecc4d7a7fa260d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/4c42ce499ce4b1c787e61082e3b13df4f30c4eaa",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}