fkie_cve-2025-39928
Vulnerability from fkie_nvd
Published
2025-10-01 08:15
Modified
2025-10-02 19:12
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
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/06418cb5a1a542a003fdb4ad8e76ea542d57cfba
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c91382328fc89f73144d5582f2d8f1dd3e41c8f7
Impacted products
Vendor Product Version


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{
  "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"
    }
  ],
  "id": "CVE-2025-39928",
  "lastModified": "2025-10-02T19:12:17.160",
  "metrics": {},
  "published": "2025-10-01T08:15:36.230",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/06418cb5a1a542a003fdb4ad8e76ea542d57cfba"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c91382328fc89f73144d5582f2d8f1dd3e41c8f7"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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