CVE-2026-64191

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Source
https://cve.org/CVERecord?id=CVE-2026-64191
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64191.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-64191
Downstream
Related
Published
2026-07-20T16:27:51Z
Modified
2026-08-31T18:26:06Z
Severity
  • 7.8 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
Summary
i2c: stub: Reject I2C block transfers with invalid length
Details

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: 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)

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().

Database specific 
{
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64191.json"
}
References

Affected packages

Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Affected ranges

Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
4710317891e4824ce1510a6b5066abbd3e917750
Fixed
7e9072dbd5f2f17934751873450d2c22080ead80
Fixed
21e87f336ac6303fed54a69b1d0d79a23b25c8d0
Fixed
3fd225f3e4cd67ec8ddab1afed9da03c7c43537c
Fixed
1c4ffe6b4f04365485ed58d64c9bb86b46fc9037
Fixed
4bd8635f28c135a08aac6badcd7d9b5cdb34335f
Fixed
5f4d2bd028ebb6e4c09a9d64842546022321d4a7
Fixed
0526931b16e5a118d367b7bfce7d797e63f7ac69
Fixed
6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64191.json"

Linux / Kernel

Package

Name
Kernel

Affected ranges

Type
ECOSYSTEM
Events
Introduced
2.6.33
Fixed
5.10.260
Type
ECOSYSTEM
Events
Introduced
5.11.0
Fixed
5.15.211
Type
ECOSYSTEM
Events
Introduced
5.16.0
Fixed
6.1.177
Type
ECOSYSTEM
Events
Introduced
6.2.0
Fixed
6.6.144
Type
ECOSYSTEM
Events
Introduced
6.7.0
Fixed
6.12.95
Type
ECOSYSTEM
Events
Introduced
6.13.0
Fixed
6.18.37
Type
ECOSYSTEM
Events
Introduced
6.19.0
Fixed
7.0.14

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64191.json"