{"id":"CVE-2026-64191","revision":"4c421c2f8c73451896fef80f8576a74f","records":[{"revision":"4c421c2f8c73451896fef80f8576a74f","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-64191","aliases":[],"title":"i2c: stub: Reject I2C block transfers with invalid length","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ni2c: stub: Reject I2C block transfers with invalid length\n\nThe I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data->block[0]\nas the transfer length. The existing check only clamps it to avoid\noverrunning the chip->words[256] register array, but does not validate\nit against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union\ni2c_smbus_data.block buffer (34 bytes total). The driver is a\ndevelopment/test tool (CONFIG_I2C_STUB=m, not built by default)\nthat must be loaded with a chip_addr= parameter.\n\nA local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl\nwith I2C_SMBUS_I2C_BLOCK_DATA and data->block[0] > 32, causing\nstub_xfer() to read or write past the end of the union\ni2c_smbus_data.block buffer:\n\n BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223)\n Read of size 1 at addr ffff88800abcfd92 by task exploit/81\n Call Trace:\n \n stub_xfer (drivers/i2c/i2c-stub.c:223)\n __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593)\n i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536)\n i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391)\n i2cdev_ioctl (drivers/i2c/i2c-dev.c:478)\n __x64_sys_ioctl (fs/ioctl.c:583)\n do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\n \n\nThe bug exists because i2c-stub implements .smbus_xfer directly,\nbypassing the I2C_SMBUS_BLOCK_MAX validation in\ni2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same\nfunction correctly validates against I2C_SMBUS_BLOCK_MAX, but the\nI2C_SMBUS_I2C_BLOCK_DATA case does not.\n\nFix by rejecting transfers with data->block[0] == 0 or\ndata->block[0] > I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with\nboth the I2C_SMBUS_BLOCK_DATA case in the same function and the\nI2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated().","state":0,"publishedAt":"2026-07-20T16:27:51.12+00:00","modifiedAt":"2026-10-19T20:28:15.069+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"drivers/i2c/i2c-stub.c\"\n ],\n \"versions\": [\n {\n \"version\": \"4710317891e4824ce1510a6b5066abbd3e917750\",\n \"lessThan\": \"7e9072dbd5f2f17934751873450d2c22080ead80\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"4710317891e4824ce1510a6b5066abbd3e917750\",\n \"lessThan\": \"21e87f336ac6303fed54a69b1d0d79a23b25c8d0\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"4710317891e4824ce1510a6b5066abbd3e917750\",\n \"lessThan\": \"3fd225f3e4cd67ec8ddab1afed9da03c7c43537c\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"4710317891e4824ce1510a6b5066abbd3e917750\",\n \"lessThan\": \"1c4ffe6b4f04365485ed58d64c9bb86b46fc9037\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"4710317891e4824ce1510a6b5066abbd3e917750\",\n \"lessThan\": \"4bd8635f28c135a08aac6badcd7d9b5cdb34335f\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"4710317891e4824ce1510a6b5066abbd3e917750\",\n \"lessThan\": \"5f4d2bd028ebb6e4c09a9d64842546022321d4a7\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"4710317891e4824ce1510a6b5066abbd3e917750\",\n \"lessThan\": \"0526931b16e5a118d367b7bfce7d797e63f7ac69\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"4710317891e4824ce1510a6b5066abbd3e917750\",\n \"lessThan\": \"6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"drivers/i2c/i2c-stub.c\"\n ],\n \"versions\": [\n {\n \"version\": \"2.6.33\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"2.6.33\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.260\",\n \"lessThanOrEqual\": \"5.10.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.211\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.177\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.144\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.95\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.37\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.0.14\",\n \"lessThanOrEqual\": \"7.0.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.1\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/7e9072dbd5f2f17934751873450d2c22080ead80","https://git.kernel.org/stable/c/21e87f336ac6303fed54a69b1d0d79a23b25c8d0","https://git.kernel.org/stable/c/3fd225f3e4cd67ec8ddab1afed9da03c7c43537c","https://git.kernel.org/stable/c/1c4ffe6b4f04365485ed58d64c9bb86b46fc9037","https://git.kernel.org/stable/c/4bd8635f28c135a08aac6badcd7d9b5cdb34335f","https://git.kernel.org/stable/c/5f4d2bd028ebb6e4c09a9d64842546022321d4a7","https://git.kernel.org/stable/c/0526931b16e5a118d367b7bfce7d797e63f7ac69","https://git.kernel.org/stable/c/6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-64191","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-64191","identifiers":["CVE-2026-64191"]},"retained":false,"historicalAffected":[]}],"coverage":[]}