{"id":"CVE-2026-64191","state":"PUBLISHED","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  <TASK>\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  </TASK>\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().","publishedAt":"2026-07-20T16:27:51.120Z","updatedAt":"2026-10-19T20:28:15.069Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"7e9072dbd5f2f17934751873450d2c22080ead80","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"21e87f336ac6303fed54a69b1d0d79a23b25c8d0","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"3fd225f3e4cd67ec8ddab1afed9da03c7c43537c","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"1c4ffe6b4f04365485ed58d64c9bb86b46fc9037","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"4bd8635f28c135a08aac6badcd7d9b5cdb34335f","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"5f4d2bd028ebb6e4c09a9d64842546022321d4a7","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"0526931b16e5a118d367b7bfce7d797e63f7ac69","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/i2c/i2c-stub.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.33","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.33","versionType":"semver"},{"version":"5.10.260","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.211","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.177","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.144","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.95","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.37","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.14","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/i2c/i2c-stub.c"]}],"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"],"weaknesses":["CWE-787"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64191.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64191","state":"PUBLISHED","datePublished":"2026-07-20T16:27:51.120Z","dateUpdated":"2026-10-19T20:28:15.069Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.040Z"},"containers":{"cna":{"title":"i2c: stub: Reject I2C block transfers with invalid length","descriptions":[{"lang":"en","value":"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  <TASK>\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  </TASK>\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()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"7e9072dbd5f2f17934751873450d2c22080ead80","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"21e87f336ac6303fed54a69b1d0d79a23b25c8d0","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"3fd225f3e4cd67ec8ddab1afed9da03c7c43537c","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"1c4ffe6b4f04365485ed58d64c9bb86b46fc9037","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"4bd8635f28c135a08aac6badcd7d9b5cdb34335f","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"5f4d2bd028ebb6e4c09a9d64842546022321d4a7","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"0526931b16e5a118d367b7bfce7d797e63f7ac69","versionType":"git"},{"version":"4710317891e4824ce1510a6b5066abbd3e917750","status":"affected","lessThan":"6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/i2c/i2c-stub.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.33","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.33","versionType":"semver"},{"version":"5.10.260","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.211","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.177","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.144","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.95","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.37","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.14","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/i2c/i2c-stub.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/7e9072dbd5f2f17934751873450d2c22080ead80"},{"url":"https://git.kernel.org/stable/c/21e87f336ac6303fed54a69b1d0d79a23b25c8d0"},{"url":"https://git.kernel.org/stable/c/3fd225f3e4cd67ec8ddab1afed9da03c7c43537c"},{"url":"https://git.kernel.org/stable/c/1c4ffe6b4f04365485ed58d64c9bb86b46fc9037"},{"url":"https://git.kernel.org/stable/c/4bd8635f28c135a08aac6badcd7d9b5cdb34335f"},{"url":"https://git.kernel.org/stable/c/5f4d2bd028ebb6e4c09a9d64842546022321d4a7"},{"url":"https://git.kernel.org/stable/c/0526931b16e5a118d367b7bfce7d797e63f7ac69"},{"url":"https://git.kernel.org/stable/c/6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable path is reached by a local process issuing I2C_SMBUS ioctls on an i2c-stub /dev/i2c-* character device; it is neither remotely nor physically reachable.\nAC:L - Once i2c-stub is loaded, the attacker controls the address, direction, length, and register contents, making the corruption deterministic without a race. The non-default module configuration defines the vulnerable deployment rather than complicating exploitation within it.\nPR:L - The attacker needs unprivileged local access to the applicable /dev/i2c-* node, but no capability or namespace-specific administrative privilege is checked anywhere along the ioctl path.\nUI:N - After the vulnerable adapter is configured, exploitation requires only attacker-issued ioctls and no action by another user.\nS:U - The corruption occurs within the host kernel and represents conventional local privilege escalation, without crossing a separate virtualization or hardware security authority.\nC:H - An oversized block write reads up to 222 bytes beyond the 34-byte stack union and persists those bytes in attacker-readable stub registers, enabling substantial kernel-stack disclosure.\nI:H - An oversized block read writes up to 222 attacker-chosen bytes beyond the stack union because the attacker can prepopulate the stub registers, enabling control-data corruption and potential kernel code execution.\nA:H - The controlled stack overwrite can corrupt stack canaries, return state, or other control data, causing a repeatable kernel oops or panic even when code execution is unsuccessful."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:39:59.861Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"5.10.260"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"5.15.211"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"6.1.177"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"6.6.144"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"6.12.95"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"6.18.37"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"7.0.14"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-64191","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:37:24.187565Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-787","lang":"en","type":"CWE","description":"CWE-787 Out-of-bounds Write"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:28:15.069Z"}}]}}}