CVE-2025-39928 (GCVE-0-2025-39928)
Vulnerability from cvelistv5
Published
2025-10-01 08:07
Modified
2025-10-01 08:07
Severity ?
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
References
Impacted products
Vendor Product Version
Linux Linux Version: c366be720235301fdadf67e6f1ea6ff32669c074
Version: c366be720235301fdadf67e6f1ea6ff32669c074
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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/i2c/busses/i2c-rtl9300.c"
          ],
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          "vendor": "Linux",
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          "vendor": "Linux",
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              "versionType": "semver"
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      ],
      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ni2c: rtl9300: ensure data length is within supported range\n\nAdd an explicit check for the xfer length to \u0027rtl9300_i2c_config_xfer\u0027\nto ensure the data length isn\u0027t within the supported range. In\nparticular a data length of 0 is not supported by the hardware and\ncauses unintended or destructive behaviour.\n\nThis limitation becomes obvious when looking at the register\ndocumentation [1]. 4 bits are reserved for DATA_WIDTH and the value\nof these 4 bits is used as N + 1, allowing a data length range of\n1 \u003c= len \u003c= 16.\n\nAffected by this is the SMBus Quick Operation which works with a data\nlength of 0. Passing 0 as the length causes an underflow of the value\ndue to:\n\n(len - 1) \u0026 0xf\n\nand effectively specifying a transfer length of 16 via the registers.\nThis causes a 16-byte write operation instead of a Quick Write. For\nexample, on SFP modules without write-protected EEPROM this soft-bricks\nthem by overwriting some initial bytes.\n\nFor completeness, also add a quirk for the zero length.\n\n[1] https://svanheule.net/realtek/longan/register/i2c_mst1_ctrl2"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-10-01T08:07:15.530Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/c91382328fc89f73144d5582f2d8f1dd3e41c8f7"
        },
        {
          "url": "https://git.kernel.org/stable/c/06418cb5a1a542a003fdb4ad8e76ea542d57cfba"
        }
      ],
      "title": "i2c: rtl9300: ensure data length is within supported range",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39928",
    "datePublished": "2025-10-01T08:07:15.530Z",
    "dateReserved": "2025-04-16T07:20:57.147Z",
    "dateUpdated": "2025-10-01T08:07:15.530Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-39928\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-10-01T08:15:36.230\",\"lastModified\":\"2025-10-02T19:12:17.160\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\ni2c: rtl9300: ensure data length is within supported range\\n\\nAdd an explicit check for the xfer length to \u0027rtl9300_i2c_config_xfer\u0027\\nto ensure the data length isn\u0027t within the supported range. In\\nparticular a data length of 0 is not supported by the hardware and\\ncauses unintended or destructive behaviour.\\n\\nThis limitation becomes obvious when looking at the register\\ndocumentation [1]. 4 bits are reserved for DATA_WIDTH and the value\\nof these 4 bits is used as N + 1, allowing a data length range of\\n1 \u003c= len \u003c= 16.\\n\\nAffected by this is the SMBus Quick Operation which works with a data\\nlength of 0. Passing 0 as the length causes an underflow of the value\\ndue to:\\n\\n(len - 1) \u0026 0xf\\n\\nand effectively specifying a transfer length of 16 via the registers.\\nThis causes a 16-byte write operation instead of a Quick Write. For\\nexample, on SFP modules without write-protected EEPROM this soft-bricks\\nthem by overwriting some initial bytes.\\n\\nFor completeness, also add a quirk for the zero length.\\n\\n[1] https://svanheule.net/realtek/longan/register/i2c_mst1_ctrl2\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/06418cb5a1a542a003fdb4ad8e76ea542d57cfba\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c91382328fc89f73144d5582f2d8f1dd3e41c8f7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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