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CVE-2026-89722 (GCVE-0-2026-89722)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:46 – Updated: 2026-09-13 06:24
VLAI
Title
PCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io()
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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < e892f05f1f790d5721cd8e3c561ed76da7e08bae (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 7a99e9c7011905734cc2739038f2a224b6be0d1f (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < dc76258d0132df1d831a5a29758bd448ca9c566e (git)
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Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 6.18.50 , ≤ 6.18.* (semver)
Unaffected: 7.2.4 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "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": [
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              "lessThan": "e892f05f1f790d5721cd8e3c561ed76da7e08bae",
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              "versionType": "git"
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              "status": "affected",
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              "versionType": "git"
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              "status": "affected",
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              "versionType": "git"
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          "product": "Linux",
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          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "2.6.12"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
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              "version": "7.2.4",
              "versionType": "semver"
            },
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              "status": "unaffected",
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                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "2.6.12",
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                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:24:09.318Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e892f05f1f790d5721cd8e3c561ed76da7e08bae"
        },
        {
          "url": "https://git.kernel.org/stable/c/7a99e9c7011905734cc2739038f2a224b6be0d1f"
        },
        {
          "url": "https://git.kernel.org/stable/c/dc76258d0132df1d831a5a29758bd448ca9c566e"
        }
      ],
      "title": "PCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io()",
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        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89722",
    "datePublished": "2026-09-11T19:46:34.427Z",
    "dateReserved": "2026-09-11T19:38:34.759Z",
    "dateUpdated": "2026-09-13T06:24:09.318Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-89722",
      "date": "2026-09-16",
      "epss": "0.00198",
      "percentile": "0.09787"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-15T01:46:08.000Z",
      "cve": "CVE-2026-89722",
      "id": "msrc_CVE-2026-89722",
      "initial_release_date": "2026-09-13T01:11:40.000Z",
      "product_status:known_not_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "PCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io()",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-89722.json",
      "version": "3"
    },
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    "redhat_vex": {
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      "cve": "CVE-2026-89722",
      "id": "CVE-2026-89722",
      "initial_release_date": "2026-09-12T16:22:50Z",
      "product_status:known_affected": "353",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89722",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89722.json",
      "version": "3"
    }
  }
}



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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

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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.


Detection rules are retrieved from Rulezet.


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.