i2c: rtl9300: ensure data length is within supported range

Summary

CVE	CVE-2025-39928
State	PUBLISHED
Assigner	Linux
Source Priority	CVE Program / NVD first with legacy fallback
Published	2025-10-01 08:15:36 UTC
Updated	2026-07-30 06:23:57 UTC
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

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.001220000 probability, percentile 0.023700000 (date 2026-07-30)

Problem Types: CWE-191 | CWE-191 CWE-191 Integer Underflow (Wrap or Wraparound)

Version	Source	Type	Score	Severity	Vector
3.1	[email protected]	Primary	5.5	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`
3.1	ADP	DECLARED	5.5	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`
3.1	416baaa9-dc9f-4396-8d5f-8c081fb06d67	Secondary	7.1	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H`
3.1	134c704f-9b21-4f2e-91b3-4a467353bcc0	Secondary	5.5	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`
3.1	CNA	DECLARED	7.1	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H`

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Type	Vendor	Product	Version	Update	Edition	Language
Operating System	Linux	Linux Kernel	All	All	All	All
Operating System	Linux	Linux Kernel	6.17	rc1	All	All
Operating System	Linux	Linux Kernel	6.17	rc2	All	All
Operating System	Linux	Linux Kernel	6.17	rc3	All	All
Operating System	Linux	Linux Kernel	6.17	rc4	All	All

Source	Vendor	Product	Version	Platforms
CNA	Linux	Linux	affected c366be720235301fdadf67e6f1ea6ff32669c074 c91382328fc89f73144d5582f2d8f1dd3e41c8f7 git	Not specified
CNA	Linux	Linux	affected c366be720235301fdadf67e6f1ea6ff32669c074 06418cb5a1a542a003fdb4ad8e76ea542d57cfba git	Not specified
CNA	Linux	Linux	affected 6.13	Not specified
CNA	Linux	Linux	unaffected 6.13 semver	Not specified
CNA	Linux	Linux	unaffected 6.16.8 6.16.* semver	Not specified
CNA	Linux	Linux	unaffected 6.17 * original_commit_for_fix	Not specified

Reference	Source	Link	Tags
git.kernel.org/stable/c/c91382328fc89f73144d5582f2d8f1dd3e41c8f7	416baaa9-dc9f-4396-8d5f-8c081fb06d67	git.kernel.org	Patch
git.kernel.org/stable/c/06418cb5a1a542a003fdb4ad8e76ea542d57cfba	416baaa9-dc9f-4396-8d5f-8c081fb06d67	git.kernel.org	Patch
CVE Program record	CVE.ORG	www.cve.org	canonical
NVD vulnerability detail	NVD	nvd.nist.gov	canonical, analysis

No vendor comments have been submitted for this CVE.

There are currently no legacy QID mappings associated with this CVE.