CVE-2026-64191
i2c: stub: Reject I2C block transfers with invalid length
Description
In the Linux kernel, the following vulnerability has been resolved: i2c: stub: Reject I2C block transfers with invalid length The I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data->block[0] as the transfer length. The existing check only clamps it to avoid overrunning the chip->words[256] register array, but does not validate it against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union i2c_smbus_data.block buffer (34 bytes total). The driver is a development/test tool (CONFIG_I2C_STUB=m, not built by default) that must be loaded with a chip_addr= parameter. A local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl with I2C_SMBUS_I2C_BLOCK_DATA and data->block[0] > 32, causing stub_xfer() to read or write past the end of the union i2c_smbus_data.block buffer: BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223) Read of size 1 at addr ffff88800abcfd92 by task exploit/81 Call Trace: <TASK> stub_xfer (drivers/i2c/i2c-stub.c:223) __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593) i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536) i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391) i2cdev_ioctl (drivers/i2c/i2c-dev.c:478) __x64_sys_ioctl (fs/ioctl.c:583) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) </TASK> The bug exists because i2c-stub implements .smbus_xfer directly, bypassing the I2C_SMBUS_BLOCK_MAX validation in i2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same function correctly validates against I2C_SMBUS_BLOCK_MAX, but the I2C_SMBUS_I2C_BLOCK_DATA case does not. Fix by rejecting transfers with data->block[0] == 0 or data->block[0] > I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with both the I2C_SMBUS_BLOCK_DATA case in the same function and the I2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated().
INFO
Published Date :
July 20, 2026, 5:18 p.m.
Last Modified :
July 20, 2026, 5:18 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Update the Linux kernel to the patched version.
- Ensure the i2c-stub driver validates transfer lengths.
- Reject transfers with invalid block lengths.
References to Advisories, Solutions, and Tools
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CVE-2026-64191.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-64191 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
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stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-64191
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2026-64191 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-64191 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 20, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '4710317891e4824ce1510a6b5066abbd3e917750', 'lessThan': '7e9072dbd5f2f17934751873450d2c22080ead80', 'versionType': 'git'}, {'status': 'affected', 'version': '4710317891e4824ce1510a6b5066abbd3e917750', 'lessThan': '21e87f336ac6303fed54a69b1d0d79a23b25c8d0', 'versionType': 'git'}, {'status': 'affected', 'version': '4710317891e4824ce1510a6b5066abbd3e917750', 'lessThan': '3fd225f3e4cd67ec8ddab1afed9da03c7c43537c', 'versionType': 'git'}, {'status': 'affected', 'version': '4710317891e4824ce1510a6b5066abbd3e917750', 'lessThan': '1c4ffe6b4f04365485ed58d64c9bb86b46fc9037', 'versionType': 'git'}, {'status': 'affected', 'version': '4710317891e4824ce1510a6b5066abbd3e917750', 'lessThan': '4bd8635f28c135a08aac6badcd7d9b5cdb34335f', 'versionType': 'git'}, {'status': 'affected', 'version': '4710317891e4824ce1510a6b5066abbd3e917750', 'lessThan': '5f4d2bd028ebb6e4c09a9d64842546022321d4a7', 'versionType': 'git'}, {'status': 'affected', 'version': '4710317891e4824ce1510a6b5066abbd3e917750', 'lessThan': '0526931b16e5a118d367b7bfce7d797e63f7ac69', 'versionType': 'git'}, {'status': 'affected', 'version': '4710317891e4824ce1510a6b5066abbd3e917750', 'lessThan': '6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e', 'versionType': 'git'}], 'programFiles': ['drivers/i2c/i2c-stub.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '2.6.33'}, {'status': 'unaffected', 'version': '0', 'lessThan': '2.6.33', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '5.10.260', 'versionType': 'semver', 'lessThanOrEqual': '5.10.*'}, {'status': 'unaffected', 'version': '5.15.211', 'versionType': 'semver', 'lessThanOrEqual': '5.15.*'}, {'status': 'unaffected', 'version': '6.1.177', 'versionType': 'semver', 'lessThanOrEqual': '6.1.*'}, {'status': 'unaffected', 'version': '6.6.144', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.95', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.37', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.0.14', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['drivers/i2c/i2c-stub.c'], 'defaultStatus': 'affected'}] Added Description In the Linux kernel, the following vulnerability has been resolved: i2c: stub: Reject I2C block transfers with invalid length The I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data->block[0] as the transfer length. The existing check only clamps it to avoid overrunning the chip->words[256] register array, but does not validate it against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union i2c_smbus_data.block buffer (34 bytes total). The driver is a development/test tool (CONFIG_I2C_STUB=m, not built by default) that must be loaded with a chip_addr= parameter. A local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl with I2C_SMBUS_I2C_BLOCK_DATA and data->block[0] > 32, causing stub_xfer() to read or write past the end of the union i2c_smbus_data.block buffer: BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223) Read of size 1 at addr ffff88800abcfd92 by task exploit/81 Call Trace: <TASK> stub_xfer (drivers/i2c/i2c-stub.c:223) __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593) i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536) i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391) i2cdev_ioctl (drivers/i2c/i2c-dev.c:478) __x64_sys_ioctl (fs/ioctl.c:583) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) </TASK> The bug exists because i2c-stub implements .smbus_xfer directly, bypassing the I2C_SMBUS_BLOCK_MAX validation in i2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same function correctly validates against I2C_SMBUS_BLOCK_MAX, but the I2C_SMBUS_I2C_BLOCK_DATA case does not. Fix by rejecting transfers with data->block[0] == 0 or data->block[0] > I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with both the I2C_SMBUS_BLOCK_DATA case in the same function and the I2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated(). Added Reference https://git.kernel.org/stable/c/0526931b16e5a118d367b7bfce7d797e63f7ac69 Added Reference https://git.kernel.org/stable/c/1c4ffe6b4f04365485ed58d64c9bb86b46fc9037 Added Reference https://git.kernel.org/stable/c/21e87f336ac6303fed54a69b1d0d79a23b25c8d0 Added Reference https://git.kernel.org/stable/c/3fd225f3e4cd67ec8ddab1afed9da03c7c43537c Added Reference https://git.kernel.org/stable/c/4bd8635f28c135a08aac6badcd7d9b5cdb34335f Added Reference https://git.kernel.org/stable/c/5f4d2bd028ebb6e4c09a9d64842546022321d4a7 Added Reference https://git.kernel.org/stable/c/6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e Added Reference https://git.kernel.org/stable/c/7e9072dbd5f2f17934751873450d2c22080ead80