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VulnerabilityPublished Updated

CVE-2026-64191: Linux kernel · Out-of-bounds Write

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.8 High · fixed in 0526931b16e5a118d367b7bfce7d797e63f7ac69 : patch Linux kernel soon.

Data as of 26 Oct 2026, 15:59 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in 0526931b16e5a118d367b7bfce7d797e63f7ac69, 6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e, 21e87f336ac6303fed54a69b1d0d79a23b25c8d0 +5
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 0526931b16e5a118d367b7bfce7d797e63f7ac69
Fixed in
  • 0526931b16e5a118d367b7bfce7d797e63f7ac69
LinuxLinuxAffected
  • ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e
Fixed in
  • 6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e
LinuxLinuxAffected
  • ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 21e87f336ac6303fed54a69b1d0d79a23b25c8d0
Fixed in
  • 21e87f336ac6303fed54a69b1d0d79a23b25c8d0
LinuxLinuxAffected
  • ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 7e9072dbd5f2f17934751873450d2c22080ead80
Fixed in
  • 7e9072dbd5f2f17934751873450d2c22080ead80
LinuxLinuxAffected
  • ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 5f4d2bd028ebb6e4c09a9d64842546022321d4a7
Fixed in
  • 5f4d2bd028ebb6e4c09a9d64842546022321d4a7
LinuxLinuxAffected
  • ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 4bd8635f28c135a08aac6badcd7d9b5cdb34335f
Fixed in
  • 4bd8635f28c135a08aac6badcd7d9b5cdb34335f

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().

References

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