CyberSecBulletin
CVE-2026-64191NVD status: Modified

Linux: Out-of-bounds Read

Published Updated By the CyberSecBulletin desk

CVE-2026-64191 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 7e9072dbd5f2f17934751873450d2c22080ead80, 21e87f336ac6303fed54a69b1d0d79a23b25c8d0, 3fd225f3e4cd67ec8ddab1afed9da03c7c43537c as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.17% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 7e9072dbd5f2f17934751873450d2c22080ead80 or 21e87f336ac6303fed54a69b1d0d79a23b25c8d0 or 3fd225f3e4cd67ec8ddab1afed9da03c7c43537c or 1c4ffe6b4f04365485ed58d64c9bb86b46fc9037, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.260 or 5.15.211 or 6.1.177 or 6.6.144, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux4710317891e4824ce1510a6b5066abbd3e917750 up to, but not including, 7e9072dbd5f2f17934751873450d2c22080ead80; 4710317891e4824ce1510a6b5066abbd3e917750 up to, but not including, 21e87f336ac6303fed54a69b1d0d79a23b25c8d0; 4710317891e4824ce1510a6b5066abbd3e917750 up to, but not including, 3fd225f3e4cd67ec8ddab1afed9da03c7c43537c; 4710317891e4824ce1510a6b5066abbd3e917750 up to, but not including, 1c4ffe6b4f04365485ed58d64c9bb86b46fc9037; 4710317891e4824ce1510a6b5066abbd3e917750 up to, but not including, 4bd8635f28c135a08aac6badcd7d9b5cdb34335f; 4710317891e4824ce1510a6b5066abbd3e917750 up to, but not including, 5f4d2bd028ebb6e4c09a9d64842546022321d4a7; 4710317891e4824ce1510a6b5066abbd3e917750 up to, but not including, 0526931b16e5a118d367b7bfce7d797e63f7ac69; 4710317891e4824ce1510a6b5066abbd3e917750 up to, but not including, 6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e; and 1 more ranges7e9072dbd5f2f17934751873450d2c22080ead80, 21e87f336ac6303fed54a69b1d0d79a23b25c8d0, 3fd225f3e4cd67ec8ddab1afed9da03c7c43537c, 1c4ffe6b4f04365485ed58d64c9bb86b46fc9037, 4bd8635f28c135a08aac6badcd7d9b5cdb34335f, 5f4d2bd028ebb6e4c09a9d64842546022321d4a7
LinuxLinux Kernel2.6.33 up to, but not including, 5.10.260; 5.11 up to, but not including, 5.15.211; 5.16 up to, but not including, 6.1.177; 6.2 up to, but not including, 6.6.144; 6.7 up to, but not including, 6.12.95; 6.13 up to, but not including, 6.18.37; 6.19 up to, but not including, 7.0.14; 7.15.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95, 6.18.37

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official 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().

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Read

The product reads data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that provides appropriate memory abstractions.

More Out-of-bounds Read vulnerabilities (CWE-125)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Read vulnerabilities

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