CVE-2025-39928

Published Oct 1, 2025

Last updated 3 months ago

CVSS medium 5.5

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: i2c: rtl9300: ensure data length is within supported range Add an explicit check for the xfer length to 'rtl9300_i2c_config_xfer' to ensure the data length isn't within the supported range. In particular a data length of 0 is not supported by the hardware and causes unintended or destructive behaviour. This limitation becomes obvious when looking at the register documentation [1]. 4 bits are reserved for DATA_WIDTH and the value of these 4 bits is used as N + 1, allowing a data length range of 1 <= len <= 16. Affected by this is the SMBus Quick Operation which works with a data length of 0. Passing 0 as the length causes an underflow of the value due to: (len - 1) & 0xf and effectively specifying a transfer length of 16 via the registers. This causes a 16-byte write operation instead of a Quick Write. For example, on SFP modules without write-protected EEPROM this soft-bricks them by overwriting some initial bytes. For completeness, also add a quirk for the zero length. [1] https://svanheule.net/realtek/longan/register/i2c_mst1_ctrl2
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Modified
Products
linux_kernel

Risk scores

CVSS 3.1

Type
Primary
Base score
5.5
Impact score
3.6
Exploitability score
1.8
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Severity
MEDIUM

Weaknesses

nvd@nist.gov
CWE-191
134c704f-9b21-4f2e-91b3-4a467353bcc0
CWE-191

Social media

Hype score
Not currently trending

  1. 🔴 #Linux Kernel, Out-of-Bounds Write Vulnerability, #CVE-2025-39928 (Critical) https://t.co/XnIBd1JkdW

    @dailycve

    11 Dec 2025

    12 Impressions

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  2. CVE-2025-39928 In the Linux kernel, the following vulnerability has been resolved: i2c: rtl9300: ensure data length is within supported range Add an explicit check for the xfer le… https://t.co/82IuSrkDgQ

    @CVEnew

    1 Oct 2025

    255 Impressions

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  3. CVE-2025-39928 Linux Kernel i2c https://t.co/fjE1EHp9MV

    @VulmonFeeds

    1 Oct 2025

    48 Impressions

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Configurations

Related CVEs

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References

Sources include official advisories and independent security research.