Linux Kernel up to 7.0.13 i2c-stub drivers/i2c/i2c-stub.c stub_xfer block out-of-bounds

CVSS Meta Temp Score
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CTI Interest Score
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8.4$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as very critical, has been found in Linux Kernel up to 7.0.13. This impacts the function stub_xfer of the file drivers/i2c/i2c-stub.c of the component i2c-stub. The manipulation of the argument block leads to out-of-bounds. This vulnerability is referenced as CVE-2026-64191. The attack can only be performed from a local environment. No exploit is available.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in Linux Kernel up to 7.0.13. This issue affects the function stub_xfer of the file drivers/i2c/i2c-stub.c of the component i2c-stub. The manipulation of the argument block with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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().

It is possible to read the advisory at git.kernel.org. The identification of this vulnerability is CVE-2026-64191 since 07/19/2026. The exploitation is known to be easy. Attacking locally is a requirement. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/05/2026).

The vulnerability scanner Nessus provides a plugin with the ID 330014 (Debian dla-4700 : linux-config-6.1 - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95, 6.18.37 or 7.0.14 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (330014) and CERT Bund (WID-SEC-2026-2427). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

  • Debian Linux
  • Open Source Linux Kernel

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.8
VulDB Meta Temp Score: 8.4

VulDB Base Score: 8.8
VulDB Temp Score: 8.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Out-of-bounds
CWE: CWE-125 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 330014
Nessus Name: Debian dla-4700 : linux-config-6.1 - security update

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.10.260/5.15.211/6.1.177/6.6.144/6.12.95/6.18.37/7.0.14

Timelineinfo

07/19/2026 CVE reserved
07/20/2026 +1 days Advisory disclosed
07/20/2026 +0 days VulDB entry created
08/05/2026 +16 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-64191 (🔒)
GCVE (CVE): GCVE-0-2026-64191
GCVE (VulDB): GCVE-100-380675
CERT Bund: WID-SEC-2026-2427 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 07/20/2026 19:25
Updated: 08/05/2026 22:35
Changes: 07/20/2026 19:25 (57), 07/27/2026 11:49 (5), 08/05/2026 22:35 (7)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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