i2c: rtl9300: ensure data length is within supported range

{
  "id": "2e9bac89a12f7e746a4cf186412f8c1db9929f9c028917b0c59dc8feaaf5e5a6",
  "url": "https://osv.dev/vulnerability/CVE-2025-39928",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "i2c: rtl9300: ensure data length is within supported range",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: i2c: rtl9300: ensure data length is within supported range Add an explicit check for the xfer length to 'rtl9300_i2c_config_xfer' to ensure the data length isn't within the supported range. In particular a data length of 0 is not supported by the hardware and causes unintended or destructive behaviour. This limitation becomes obvious when looking at the register documentation [1]. 4 bits are reserved for DATA_WIDTH and the value of these 4 bits is used as N + 1, allowing a data length range of 1 <= len <= 16. Affected by this is the SMBus Quick Operation which works with a data length of 0. Passing 0 as the length causes an underflow of the value due to: (len - 1) & 0xf and effectively specifying a transfer length of 16 via the registers. This causes a 16-byte write operation instead of a Quick Write. For example, on SFP modules without write-protected EEPROM this soft-bricks them by overwriting some initial bytes. For completeness, also add a quirk for the zero length. [1] https://svanheule.net/realtek/longan/register/i2c_mst1_ctrl2",
    "evidence": "osv:CVE-2025-39928",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.16.8",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2025-39928",
      "aliases": [
        "CVE-2025-39928"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "c366be720235301fdadf67e6f1ea6ff32669c074"
                },
                {
                  "fixed": "c91382328fc89f73144d5582f2d8f1dd3e41c8f7"
                },
                {
                  "fixed": "06418cb5a1a542a003fdb4ad8e76ea542d57cfba"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39928.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.16.8"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39928.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.044120156Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/06418cb5a1a542a003fdb4ad8e76ea542d57cfba",
        "https://git.kernel.org/stable/c/c91382328fc89f73144d5582f2d8f1dd3e41c8f7",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39928.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-39928",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39928.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-39928",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504433,
  "published_at": "2025-10-01T08:07:15.53+00:00"
}