{"api_version":"1","generated_at":"2026-08-05T14:06:47+00:00","cve":"CVE-2025-39928","urls":{"html":"https://cve.report/CVE-2025-39928","api":"https://cve.report/api/cve/CVE-2025-39928.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2025-39928","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2025-39928"},"summary":{"title":"i2c: rtl9300: ensure data length is within supported range","description":"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 'rtl9300_i2c_config_xfer'\nto ensure the data length isn't 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 <= len <= 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) & 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","state":"PUBLISHED","assigner":"Linux","published_at":"2025-10-01 08:15:36","updated_at":"2026-07-30 06:23:57"},"problem_types":["CWE-191","CWE-191 CWE-191 Integer Underflow (Wrap or 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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 <= len <= 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) & 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","Type":"Description","Title":"i2c: rtl9300: ensure data length is within supported range"}]}}}