CVE-2025-38425: Linux Kernel I2C Tegra SMBUS Block Read Vulnerability

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CVE-2025-38425: Linux Kernel I2C Tegra Driver Vulnerability in SMBUS Block Read

Welcome to a deep dive into CVE-2025-38425, a vulnerability discovered in the Linux kernel's I2C Tegra driver. This issue specifically affects the SMBUS block read functionality and could potentially lead to unexpected behavior. Understanding this vulnerability is crucial for anyone managing or developing on Linux systems.

Vulnerability Details

  • CVE ID: CVE-2025-38425
  • Description: The Linux kernel's I2C Tegra driver has a vulnerability in the SMBUS block read functionality. The driver does not properly check the message length returned by the device during an SMBUS block read. If the device returns a message length of '0' or a value greater than the maximum allowed bytes, the driver should not continue reading.
  • CVSS Score and Vector: Currently awaiting analysis. However, given the nature of the flaw, it could potentially lead to a denial-of-service or other unexpected behavior depending on how the invalid data is processed.
  • Exploit Requirements: An attacker would need to have control over an I2C device connected to the Tegra I2C controller to trigger this vulnerability. They would then need to manipulate the device to return an invalid length during an SMBUS block read.
  • Affected Vendor, Product, Version: Linux Kernel, versions prior to the fix being applied. The specific affected versions depend on when the patch was backported to various kernel releases.
  • CWE: CWE-125 - Out-of-bounds Read. This means that the code attempts to read data beyond the boundaries of the allocated buffer. This can lead to crashes, information disclosure, or other unexpected behavior.

Timeline of Events

  • 2025-07-25: CVE-2025-38425 Published.
  • [Date]: Patch submitted to the Linux kernel mailing list. (Date from Git commits in references)
  • [Date]: Patch merged into the mainline kernel. (Date from Git commits in references)

Exploitability & Real-World Risk

The exploitability of this vulnerability depends heavily on the context of the I2C bus. If the I2C bus is only connected to trusted devices, the risk is relatively low. However, if the I2C bus is exposed to external devices or devices that could be compromised, the risk is higher. In a real-world attack scenario, a compromised device could send an invalid length during an SMBUS block read, potentially causing the system to crash or behave unpredictably.

Recommendations

  • Apply the Patch: The most important recommendation is to apply the patch that fixes this vulnerability. This patch is available in the Linux kernel source tree and should be included in future kernel releases.
  • Monitor I2C Traffic: If you are concerned about this vulnerability, you can monitor I2C traffic for suspicious activity. This can help you detect and prevent attacks before they cause damage.
  • Secure I2C Devices: Ensure that all devices connected to the I2C bus are properly secured. This includes using strong passwords, keeping firmware up to date, and implementing other security measures.

Technical Insight

The vulnerability lies in the `i2c: tegra: check msg length in SMBUS block read`. The fix ensures the driver correctly validates the length of the SMBUS block read message. Prior to the fix, the driver would continue reading even if the length was invalid, leading to a potential out-of-bounds read. The patch adds a check to ensure that the length is within the allowed bounds before proceeding with the read operation. This prevents the driver from reading beyond the allocated buffer and mitigates the vulnerability.

Credit to Researcher(s)

The original discoverer(s) are not explicitly mentioned in the provided information. Credit goes to the Linux Kernel developers who identified and fixed the flaw.

References

Tags

#Linux #Kernel #I2C #SMBUS #Tegra #CVE-2025-38425 #Security

Summary: CVE-2025-38425 describes a vulnerability in the Linux kernel's I2C Tegra driver related to SMBUS block reads. The driver fails to validate message lengths received from devices, potentially leading to out-of-bounds reads and unpredictable system behavior. A patch is available to address this issue.

CVE ID: CVE-2025-38425

Risk Analysis: The risk depends on the exposure of the I2C bus. If the bus is exposed to potentially malicious devices, the risk is higher, potentially causing instability or unexpected system behavior.

Recommendation: Apply the available patch to the Linux kernel to properly validate SMBUS block read message lengths.

Timeline

  • 2025-07-25: CVE-2025-38425 Published

References

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