CVE-2024-38541: Linux Kernel Buffer Overflow Vulnerability

CVE-2024-38541 Overview

CVE-2024-38541 is a buffer overflow vulnerability in the Linux kernel's Device Tree (OF) module subsystem. The vulnerability exists in the of_modalias() function, which fails to properly validate buffer boundaries when constructing module alias strings. When the provided buffer is too small for the first snprintf() call, the len parameter becomes negative, causing the str pointer to reference memory beyond the buffer's allocated end.

Critical Impact

This buffer overflow vulnerability in the Linux kernel can potentially allow attackers to corrupt kernel memory, leading to system crashes, denial of service, or arbitrary code execution with kernel-level privileges.

Affected Products

• Linux Kernel (multiple versions)
• Debian Linux (LTS releases)
• Systems utilizing Device Tree (OF) module functionality

Discovery Timeline

• June 19, 2024 - CVE-2024-38541 published to NVD
• November 3, 2025 - Last updated in NVD database

Technical Details for CVE-2024-38541

Vulnerability Analysis

The vulnerability resides in the of_modalias() function within the Linux kernel's Device Tree module subsystem. This function is responsible for generating module alias strings used for automatic kernel module loading based on device tree node properties.

The core issue stems from inadequate buffer size validation. When of_modalias() is called with a buffer that is insufficient for even the initial snprintf() operation, a critical boundary condition occurs. The snprintf() function returns the number of characters that would have been written if the buffer were large enough, regardless of actual buffer capacity. When this return value exceeds the buffer size, the subsequent length calculation produces a negative value. This negative length then causes pointer arithmetic to move the str pointer past the buffer's valid memory region.

The vulnerability was addressed by implementing proper overflow checks after both the initial snprintf() call and the subsequent strlen() operation, with correct accounting for the terminating NUL character.

Root Cause

The root cause is a classic buffer overflow condition resulting from improper bounds checking in string manipulation operations. The of_modalias() function did not verify that the buffer provided was sufficient before proceeding with string construction. Specifically:

1. The return value from snprintf() was not validated against the actual buffer capacity
2. No check existed to ensure the len parameter remained non-negative after the first snprintf() call
3. The boundary check after strlen() did not properly account for the terminating NUL character

Attack Vector

The vulnerability is classified with a network attack vector, indicating that exploitation could potentially be triggered remotely under specific conditions. An attacker would need to influence the buffer size or contents passed to of_modalias(). While direct exploitation typically requires local access or kernel module loading capabilities, the network vector classification suggests scenarios where network-controlled data could trigger the vulnerable code path.

Exploitation would involve:

1. Triggering a call to of_modalias() with a deliberately undersized buffer
2. Causing the function to write beyond allocated memory boundaries
3. Potentially overwriting adjacent kernel memory structures
4. Achieving denial of service or, in sophisticated attacks, code execution

The vulnerability mechanism involves the following sequence: when a buffer too small for the modalias string is provided, snprintf() returns the theoretical length needed, which exceeds the actual buffer size. Subtracting this from the original length creates a negative value, and pointer arithmetic with this negative length moves the write position before the buffer start or wraps around, depending on implementation. Subsequent operations then corrupt adjacent memory regions.

Detection Methods for CVE-2024-38541

Indicators of Compromise

• Unexpected kernel panics or oops messages related to Device Tree or module loading subsystems
• Memory corruption warnings in kernel logs referencing of_modalias or related OF module functions
• System instability during device enumeration or module auto-loading operations

Detection Strategies

• Monitor kernel logs for buffer overflow warnings, memory corruption events, or crashes in the OF module subsystem
• Implement kernel address sanitizer (KASAN) in development and testing environments to detect out-of-bounds memory access
• Deploy SentinelOne Singularity Platform for real-time kernel exploit detection and behavioral monitoring of Linux systems

Monitoring Recommendations

• Enable kernel auditing to track module loading events and Device Tree operations
• Configure alerting for repeated kernel crashes or unexpected reboots that may indicate exploitation attempts
• Utilize SentinelOne's Linux agent to monitor for anomalous kernel behavior patterns associated with buffer overflow exploitation

How to Mitigate CVE-2024-38541

Immediate Actions Required

• Update to a patched Linux kernel version that includes the buffer overflow fix for of_modalias()
• Review and apply security updates from your Linux distribution vendor (e.g., Debian LTS advisories)
• Prioritize patching systems that process untrusted Device Tree data or have elevated exposure to module loading operations

Patch Information

The Linux kernel maintainers have released patches addressing this vulnerability. The fix adds proper buffer overflow checks after the first snprintf() call and corrects the boundary validation following strlen() to properly account for the terminating NUL character.

Patches are available through the following kernel git commits:

• Kernel Git Commit c/0b0d570
• Kernel Git Commit c/4679544
• Kernel Git Commit c/5d59fd63
• Kernel Git Commit c/733e627
• Kernel Git Commit c/c7f24b7
• Kernel Git Commit c/cf7385cb
• Kernel Git Commit c/e45b693
• Kernel Git Commit c/ee33202

Debian users should reference the Debian LTS Announcement May 2025 and Debian LTS Announcement Oct 2025 for distribution-specific patches.

Workarounds

• Limit access to kernel module loading functionality to trusted administrators only
• Implement strict access controls on systems that process Device Tree overlays or configurations from external sources
• Consider using kernel lockdown mode where applicable to restrict dangerous kernel operations

# Check current kernel version
uname -r

# Update kernel on Debian-based systems
sudo apt update && sudo apt upgrade linux-image-$(uname -r | sed 's/-amd64//')-amd64

# Verify kernel module loading restrictions
cat /proc/sys/kernel/modules_disabled