CVE-2024-26593: Linux Kernel Buffer Overflow Vulnerability

CVE-2024-26593 Overview

CVE-2024-26593 is an out-of-bounds read vulnerability in the Linux kernel's i2c-i801 driver that handles block process call transactions for Intel SMBus controllers. The vulnerability arises from a missing block buffer index reset operation, causing the driver to read from an incorrect portion of the block buffer during incoming data retrieval. This flaw can lead to information disclosure and potential system instability.

Critical Impact

Local attackers with low privileges can exploit this vulnerability to read sensitive kernel memory data or cause denial of service through improper buffer access in the i2c-i801 driver.

Affected Products

• Linux Kernel (multiple versions)
• Systems with Intel SMBus controllers using the i2c-i801 driver
• Debian and Fedora Linux distributions with vulnerable kernel versions

Discovery Timeline

• February 23, 2024 - CVE-2024-26593 published to NVD
• November 4, 2025 - Last updated in NVD database

Technical Details for CVE-2024-26593

Vulnerability Analysis

This vulnerability exists in the i2c-i801 driver's implementation of block process call transactions. According to Intel datasheets, the SMBus block buffer index must be reset twice during block process call operations: once before writing outgoing data to the buffer, and again before reading incoming data from the buffer. The driver implementation was missing this second reset operation.

The flaw is classified as CWE-125 (Out-of-bounds Read), which occurs when software reads data past the end of the intended buffer. In this case, because the buffer index is not properly reset before reading, the driver reads from an incorrect memory offset, potentially accessing data outside the intended buffer boundaries.

Root Cause

The root cause is an incomplete implementation of the SMBus block process call protocol in the i2c-i801 driver. The Intel hardware specification requires the block buffer index to be reset at two specific points during a block process call transaction. The driver correctly performed the first reset before writing outgoing data but failed to perform the second reset before reading incoming data. This oversight causes the read operation to start at whatever index position remained after the write operation, rather than at the beginning of the incoming data buffer.

Attack Vector

The vulnerability requires local access to exploit, as an attacker must be able to interact with the i2c-i801 driver through the I2C subsystem. A local user with appropriate permissions to access I2C devices could potentially trigger block process call transactions that expose kernel memory contents through the incorrectly read buffer data. The attack does not require user interaction and can be performed with low privileges, potentially allowing unauthorized access to sensitive kernel memory or causing system instability through corrupted data reads.

Detection Methods for CVE-2024-26593

Indicators of Compromise

• Unusual kernel log messages related to i2c-i801 driver operations or SMBus transactions
• Unexpected data corruption in applications using I2C devices connected via Intel SMBus controllers
• System instability or crashes associated with I2C subsystem operations
• Anomalous memory access patterns in kernel space related to the i2c-i801 module

Detection Strategies

• Monitor system logs for i2c-i801 driver errors or warnings using dmesg | grep -i i801
• Implement kernel auditing to track I2C device access and transaction patterns
• Deploy endpoint detection solutions capable of monitoring kernel module behavior and memory access anomalies
• Use kernel debugging tools to detect out-of-bounds read attempts in the i2c subsystem

Monitoring Recommendations

• Enable enhanced kernel logging for the I2C subsystem to capture detailed transaction information
• Configure SentinelOne agents to monitor for suspicious kernel module activity and memory access patterns
• Establish baseline behavior for I2C device interactions to identify anomalous transaction patterns
• Regularly audit systems for the presence of vulnerable kernel versions

How to Mitigate CVE-2024-26593

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the fix for CVE-2024-26593
• For Debian-based systems, apply updates referenced in the Debian LTS Announcement
• For Fedora systems, apply updates from the Fedora Package Announcement
• Restart affected systems after kernel updates to ensure the patched driver is loaded

Patch Information

The vulnerability has been fixed through multiple kernel commits across various stable branches. The patches add the missing second block buffer index reset before reading incoming data during block process call transactions. Relevant commits include:

• Kernel commit 1f8d0691c505
• Kernel commit 491528935c9c
• Kernel commit 609c7c1cc976
• Kernel commit 6be99c51829b
• Kernel commit 7a14b8a477b8
• Kernel commit c1c9d0f6f7f1
• Kernel commit d074d5ff5ae7

Workarounds

• If immediate patching is not possible, consider temporarily blacklisting the i2c-i801 module if the Intel SMBus functionality is not required
• Restrict access to I2C devices by tightening permissions on /dev/i2c-* device nodes
• Implement strict access controls to limit which users and processes can interact with I2C subsystem
• Monitor I2C device access closely and investigate any unexpected block process call transactions

# Temporary workaround: Blacklist i2c-i801 module if not needed
echo "blacklist i2c-i801" | sudo tee /etc/modprobe.d/blacklist-i2c-i801.conf
sudo update-initramfs -u
# Note: This will disable Intel SMBus functionality - only use if SMBus is not required

# Check current kernel version
uname -r

# Verify if i2c-i801 module is loaded
lsmod | grep i2c_i801