FKIE_CVE-2026-89722

Vulnerability from fkie_nvd - Published: 2026-09-11 20:20 - Updated: 2026-10-19 09:18
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: PCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io() pci_write_legacy_io() loads 4 bytes from the kernfs write buffer regardless of how many bytes userspace wrote: if (count != 1 && count != 2 && count != 4) return -EINVAL; return pci_legacy_write(bus, off, *(u32 *)buf, count); kernfs_fop_write_iter() allocates the buffer with kmalloc(len + 1), so a 1-byte write to the legacy_io sysfs file allocates 2 bytes and the unconditional u32 load reads up to 2 bytes past the end of the allocation, which KASAN reports as a slab-out-of-bounds read. Similarly, a 2-byte write overreads by 1 byte. Thus, read only the number of bytes requested using get_unaligned_le16() and get_unaligned_le32() for the 2 and 4 byte cases, interpreting the buffer as little-endian to match the byte ordering of PCI I/O port space. The PowerPC implementation previously compensated for the generic code's native-endian 32-bit load by shifting the value into place for the 1 and 2 byte cases. The shifts were only correct on big-endian kernels. On little-endian PowerPC (POWER8 and later), they extracted the wrong bytes, so a 1-byte write wrote an out-of-bounds byte instead of the requested value. On big-endian, the native load also caused out_le16() and out_le32() to reverse the user's bytes on the wire for 2 and 4 byte writes. The little-endian helpers resolve both issues, so the shifts are removed. No changes are needed for the Alpha platform. The legacy_io file is root-only and exists only on Alpha and PowerPC, the two architectures that define HAVE_PCI_LEGACY.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7a99e9c7011905734cc2739038f2a224b6be0d1f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dc76258d0132df1d831a5a29758bd448ca9c566e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e892f05f1f790d5721cd8e3c561ed76da7e08bae
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/powerpc/kernel/pci-common.c",
            "drivers/pci/pci-sysfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "e892f05f1f790d5721cd8e3c561ed76da7e08bae",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "7a99e9c7011905734cc2739038f2a224b6be0d1f",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "dc76258d0132df1d831a5a29758bd448ca9c566e",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/powerpc/kernel/pci-common.c",
            "drivers/pci/pci-sysfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
            {
              "lessThan": "2.6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nPCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io()\n\npci_write_legacy_io() loads 4 bytes from the kernfs write buffer\nregardless of how many bytes userspace wrote:\n\n  if (count != 1 \u0026\u0026 count != 2 \u0026\u0026 count != 4)\n          return -EINVAL;\n\n  return pci_legacy_write(bus, off, *(u32 *)buf, count);\n\nkernfs_fop_write_iter() allocates the buffer with kmalloc(len + 1),\nso a 1-byte write to the legacy_io sysfs file allocates 2 bytes and\nthe unconditional u32 load reads up to 2 bytes past the end of the\nallocation, which KASAN reports as a slab-out-of-bounds read.\nSimilarly, a 2-byte write overreads by 1 byte.\n\nThus, read only the number of bytes requested using get_unaligned_le16()\nand get_unaligned_le32() for the 2 and 4 byte cases, interpreting the\nbuffer as little-endian to match the byte ordering of PCI I/O port\nspace.\n\nThe PowerPC implementation previously compensated for the generic\ncode\u0027s native-endian 32-bit load by shifting the value into place\nfor the 1 and 2 byte cases.  The shifts were only correct on\nbig-endian kernels.\n\nOn little-endian PowerPC (POWER8 and later), they extracted the wrong\nbytes, so a 1-byte write wrote an out-of-bounds byte instead of the\nrequested value.  On big-endian, the native load also caused out_le16()\nand out_le32() to reverse the user\u0027s bytes on the wire for 2 and 4 byte\nwrites.  The little-endian helpers resolve both issues, so the shifts\nare removed.\n\nNo changes are needed for the Alpha platform.\n\nThe legacy_io file is root-only and exists only on Alpha and PowerPC,\nthe two architectures that define HAVE_PCI_LEGACY."
    }
  ],
  "id": "CVE-2026-89722",
  "lastModified": "2026-10-19T09:18:12.380",
  "metrics": {},
  "published": "2026-09-11T20:20:01.370",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7a99e9c7011905734cc2739038f2a224b6be0d1f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dc76258d0132df1d831a5a29758bd448ca9c566e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e892f05f1f790d5721cd8e3c561ed76da7e08bae"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.