CVE-2026-23197: Linux Kernel i2c imx DoS Vulnerability

CVE-2026-23197 Overview

A vulnerability has been identified in the Linux kernel's i2c-imx driver where improper state handling in the block data length handler can lead to buffer overruns and system crashes. When a block read returns an invalid length (zero or greater than I2C_SMBUS_BLOCK_MAX), the length handler correctly sets the state to IMX_I2C_STATE_FAILED. However, the i2c_imx_master_isr() interrupt service routine unconditionally overwrites this error state with IMX_I2C_STATE_READ_CONTINUE, causing an endless read loop that overruns buffers and crashes the system.

Critical Impact

This vulnerability can cause system crashes through buffer overruns when malicious or malformed I2C block read responses are processed, potentially affecting embedded systems and devices using the i.MX I2C subsystem.

Affected Products

• Linux kernel with i2c-imx driver enabled
• Systems using NXP i.MX processors with SMBus block read operations
• Embedded Linux platforms utilizing the IMX I2C subsystem

Discovery Timeline

• 2026-02-14 - CVE CVE-2026-23197 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-23197

Vulnerability Analysis

This vulnerability represents a state machine logic flaw in the Linux kernel's i2c-imx driver. The core issue lies in the interrupt service routine (i2c_imx_master_isr()) which fails to respect error states set by earlier processing stages.

During normal I2C block read operations, the driver validates the received data length. When the length is invalid (either zero or exceeding I2C_SMBUS_BLOCK_MAX), the length handler appropriately transitions the state machine to IMX_I2C_STATE_FAILED to halt further processing. However, the interrupt handler subsequently executes and unconditionally overwrites this state with IMX_I2C_STATE_READ_CONTINUE, effectively ignoring the error condition.

This creates an endless read loop where the driver continuously attempts to read more data than the buffer can accommodate, leading to out-of-bounds memory writes and ultimately a kernel crash.

Root Cause

The root cause is a missing guard condition in the i2c_imx_master_isr() function. The interrupt service routine performs state transitions without first checking whether the current state indicates an error condition that should be preserved. This oversight allows the ISR to override critical error states, breaking the intended error handling flow of the driver's state machine.

Attack Vector

An attacker with access to a malicious or compromised I2C peripheral device could exploit this vulnerability by responding to SMBus block read requests with invalid length values. When the i.MX I2C master receives such a response, the driver enters the vulnerable code path:

1. The master initiates a block read request to an I2C slave device
2. The slave responds with an invalid block length (0 or > 32 bytes)
3. The length handler detects the error and sets IMX_I2C_STATE_FAILED
4. The ISR executes and overwrites the state to IMX_I2C_STATE_READ_CONTINUE
5. The driver continues reading indefinitely, overrunning memory buffers
6. System crash occurs due to memory corruption

This attack requires physical or logical access to the I2C bus to inject malicious responses, limiting the attack surface primarily to scenarios involving compromised peripherals or physical access to the target system.

Detection Methods for CVE-2026-23197

Indicators of Compromise

• Kernel panic or oops messages referencing the i2c_imx driver or i2c_imx_master_isr function
• System crashes during I2C communication operations on i.MX-based platforms
• Memory corruption errors or unexpected buffer overruns in kernel logs related to I2C subsystems
• Repeated I2C read operations that never complete, visible in dmesg output

Detection Strategies

• Monitor kernel logs for stack traces involving i2c-imx.c or related driver components
• Implement kernel module integrity monitoring to detect abnormal driver behavior
• Deploy runtime memory safety tools such as KASAN (Kernel Address Sanitizer) to catch buffer overruns
• Use I2C bus analyzers to detect anomalous block read responses with invalid lengths

Monitoring Recommendations

• Enable kernel crash dump collection to capture diagnostic information during failures
• Configure syslog monitoring for I2C-related kernel messages on affected systems
• Implement health checks for systems heavily reliant on I2C communication
• Monitor for unusual system instability patterns on embedded i.MX platforms

How to Mitigate CVE-2026-23197

Immediate Actions Required

• Update the Linux kernel to a patched version containing the fix for this vulnerability
• Review deployed systems for usage of the i2c-imx driver and prioritize patching accordingly
• Consider temporarily disabling non-essential I2C peripherals on critical systems until patching is complete
• Implement physical security measures to prevent unauthorized I2C bus access

Patch Information

The Linux kernel maintainers have released patches to address this vulnerability. The fix adds a guard condition to the state transition in i2c_imx_master_isr() to preserve error states set by the length handler. The patched code checks the current state before overwriting, ensuring that IMX_I2C_STATE_FAILED is not inadvertently replaced.

Relevant kernel commits are available for review:

• Kernel Git Commit Review
• Kernel Git Commit Review

Workarounds

• Restrict physical access to I2C buses on affected systems to prevent malicious peripheral connections
• Validate I2C peripherals connected to affected systems to ensure they respond with valid block lengths
• Consider using alternative I2C drivers if available for your platform until patches can be applied
• Implement I2C bus filtering or monitoring at the hardware level where feasible

# Check if the vulnerable i2c-imx driver is loaded
lsmod | grep i2c_imx

# View current kernel version to assess patch status
uname -r

# Review I2C-related kernel messages for signs of exploitation
dmesg | grep -i i2c