CVE-2025-39928

Medium

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

Package Linux Kernel
Published 2025-10-01
Last modified 2026-01-14
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

5.5

out of 10
Medium
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness type

CWE-191

CVE-2025-39928 is classified as CWE-191

See CWE-191 on MITRE CWE for full details on this weakness type.

Affected versions

Linux kernel versions 6.13 and later are affected. Fixed in 6.16.8, 6.17 and their respective stable series.

Affected from
≥ 6.13
Fixed in
✓ 6.16.8 6.16.x ✓ 6.17

References

The following references provide additional information about CVE-2025-39928 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

Frequently asked questions

  • What is CVE-2025-39928?

    CVE-2025-39928 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 . It affects Linux kernel versions from 6.13 onward and has been patched in 6.16.8 and 6.17. CVE-2025-39928 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2025-39928?

    CVE-2025-39928 has a CVSS score of 5.5 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H .

  • Is there a patch available for CVE-2025-39928?

    Yes — CVE-2025-39928 has been patched. Fixed versions include 6.16.8 and 6.17. If you are running Linux kernel 6.13 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2025-39928 actively exploited?

    No — CVE-2025-39928 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

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