7.8

CVE-2026-64191: i2c: stub: Reject I2C block transfers with invalid length

Modified
AliasesUBUNTU-CVE-2026-64191DEBIAN-CVE-2026-64191
Published 20-07-2026Last modified 19-10-2026

Vulnerability summary

CVE-2026-64191 is a high (CVSS 7.8) Out-of-bounds Read vulnerability in linux. EPSS estimates a 0.17% chance of exploitation in the next 30 days, higher than 5.7% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
7.8/10
010
High · v3.1 (CVE.org)
EPSS score
0.17%
0%100%
Low · +0.04 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 47 · Related 32
MGASA-2026-0312OPENSUSE-SU-2026:21555-1RHSA-2026:59723RHSA-2026:59737RHSA-2026:59821RHSA-2026:65708

Timeline

  1. 20-07-2026
    PublishedVulnerability first disclosed.
  2. 19-10-2026
    Last modifiedVulnerability information updated.

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().

CVSS metrics

5 scores · 4 sources · 2 versions

EPSS trend

Probability

0.17%

Chance of exploitation in the next 30 days

Percentile

6%

Versus all other CVEs

30-day change

Increase +0.04 pp

From 0.13% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu169 products
  • linuxAll versions (No fix recorded) | < 5.15.0-198.208 | < 6.8.0-147.147 | < 7.0.0-31.31
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded) | < 5.15.0-1117.124 | < 6.8.0-1067.70 | < 7.0.0-1012.12
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 7e9072dbd5f2f17934751873450d2c22080ead80 | ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 21e87f336ac6303fed54a69b1d0d79a23b25c8d0 | ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 3fd225f3e4cd67ec8ddab1afed9da03c7c43537c | ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 1c4ffe6b4f04365485ed58d64c9bb86b46fc9037 | ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 4bd8635f28c135a08aac6badcd7d9b5cdb34335f | ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 5f4d2bd028ebb6e4c09a9d64842546022321d4a7 | ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 0526931b16e5a118d367b7bfce7d797e63f7ac69 | ≥ 4710317891e4824ce1510a6b5066abbd3e917750, < 6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e | 2.6.33
  • linux_kernel≥ 2.6.33, < 5.10.260 | ≥ 5.11, < 5.15.211 | ≥ 5.16, < 6.1.177 | ≥ 6.2, < 6.6.144 | ≥ 6.7, < 6.12.95 | ≥ 6.13, < 6.18.37 | ≥ 6.19, < 7.0.14 | 7.1:rc1 | 7.1:rc2
Debian1 product
  • linux< 6.1.177-1 | < 6.12.95-1 | < 7.0.14-1

3 vendors · 172 products

References

32 links
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