CVE-2025-39928

SFP module corruption via transfer-length underflow

Published Oct 1, 2025 · Updated Aug 5, 2026

Integer underflow in the Linux rtl9300 I2C driver allows local users to corrupt SFP EEPROM data through zero-length SMBus writes. rtl9300_i2c_config_xfer computes (len - 1) & 0xf without rejecting len=0, programming the controller for 16 bytes instead of a Quick Write. Exploitation requires local low-privileged access, the rtl9300 controller, and an attached SFP module with a non-write-protected EEPROM; overwritten initial bytes can leave that module unusable.

CVSS severity5.5
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer underflow in the Linux rtl9300 I2C driver allows local users to corrupt SFP EEPROM data through zero-length SMBus writes. rtl9300_i2c_config_xfer computes (len - 1) & 0xf without rejecting len=0, programming the controller for 16 bytes instead of a Quick Write. Exploitation requires local low-privileged access, the rtl9300 controller, and an attached SFP module with a non-write-protected EEPROM; overwritten initial bytes can leave that module unusable.

The record

CVE
CVE-2025-39928
Published
Oct 1, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-191, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 1, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.13
  2. Affected versionversion=c366be720235301fdadf67e6f1ea6ff32669c074 <06418cb5a1a542a003fdb4ad8e76ea542d57cfba
  3. Affected versionversion=c366be720235301fdadf67e6f1ea6ff32669c074 <c91382328fc89f73144d5582f2d8f1dd3e41c8f7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.13; version=c366be720235301fdadf67e6f1ea6ff32669c074 <06418cb5a1a542a003fdb4ad8e76ea542d57cfba; version=c366be720235301fdadf67e6f1ea6ff32669c074 <c91382328fc89f73144d5582f2d8f1dd3e41c8f7

Published CVSS scores

5.5NISTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-191Integer Underflow (Wrap or Wraparound)
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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