CVE-2024-38541 Overview
CVE-2024-38541 is a buffer overflow vulnerability in the Linux kernel's Open Firmware (OF) device tree subsystem. The flaw resides in the of_modalias() function, which constructs module alias strings for device tree nodes. When the destination buffer is too small for the first snprintf() call, the length parameter becomes negative and the string pointer advances beyond the buffer boundary. This results in out-of-bounds memory access during subsequent operations. The vulnerability is classified under [CWE-120] (Buffer Copy without Checking Size of Input) and affects multiple Linux kernel branches across stable and long-term support releases.
Critical Impact
Buffer overflow in of_modalias() can lead to kernel memory corruption, potentially enabling denial of service or arbitrary code execution in kernel context.
Affected Products
- Linux Kernel (multiple stable branches prior to patched commits)
- Debian GNU/Linux (addressed via Debian LTS advisories)
- Distributions shipping vulnerable kernel versions on systems using Open Firmware device tree parsing
Discovery Timeline
- 2024-06-19 - CVE-2024-38541 published to NVD
- 2025-05 - Debian LTS announcement addressing the issue
- 2025-10 - Additional Debian LTS announcement issued
- 2025-11-03 - Last updated in NVD database
Technical Details for CVE-2024-38541
Vulnerability Analysis
The of_modalias() function in the Linux kernel's drivers/of/device.c builds module alias strings from device tree compatible properties. The function uses snprintf() to write into a caller-provided buffer and updates len and str pointers to track remaining space. The vulnerable logic fails to verify whether the first snprintf() call exceeded the buffer's capacity before continuing to use the pointer.
When the buffer is too small for the initial formatted output, snprintf() returns the number of bytes that would have been written, which exceeds the buffer length. The code then subtracts this value from len, producing a negative result. Subsequent operations advance str beyond the end of the buffer, and further writes occur in out-of-bounds memory. The patch adds a bounds check after the first snprintf() and corrects the post-strlen() validation to account for the terminating NUL byte.
Root Cause
The root cause is missing return-value validation after snprintf(). The function trusted the formatted output to fit without verifying the truncation indicator. This is a classic boundary condition error where arithmetic on size variables produces negative or wraparound values, leading to pointer arithmetic that escapes the intended buffer.
Attack Vector
Triggering the condition requires the kernel to process a device tree node whose compatible string set produces formatted output larger than the caller's buffer. On systems where device tree data can be influenced by untrusted firmware images, virtualized device trees, or hot-pluggable hardware descriptions, an attacker controlling these inputs may induce the overflow. Successful exploitation can corrupt adjacent kernel memory structures.
No verified public proof-of-concept exploit code is available for this vulnerability. Refer to the upstream kernel commits for the precise patch logic.
Detection Methods for CVE-2024-38541
Indicators of Compromise
- Unexpected kernel oops or panic messages referencing of_modalias or device tree parsing routines in dmesg and kernel logs
- KASAN (Kernel Address Sanitizer) reports flagging out-of-bounds writes in the OF subsystem
- Module loading failures or corrupted modalias sysfs entries under /sys/devices/
Detection Strategies
- Inventory running kernel versions across Linux hosts and compare against the patched commit hashes (0b0d5701, 46795440, 5d59fd63, 733e6278, c7f24b7d, cf7385cb, e45b6936, ee332023)
- Enable KASAN in test or staging environments to catch out-of-bounds access during device tree processing
- Monitor for unexplained kernel crashes on platforms that consume device tree blobs at runtime
Monitoring Recommendations
- Forward kernel ring buffer and journalctl -k output to a centralized logging platform for anomaly review
- Track package versions of linux-image-* against vendor security advisories from Debian LTS and upstream stable trees
- Audit any process or workload that loads custom device tree overlays, including container runtimes that mount hardware descriptions
How to Mitigate CVE-2024-38541
Immediate Actions Required
- Apply vendor-supplied kernel updates from your Linux distribution as soon as they are available
- Reboot systems after kernel package upgrades to load the patched image
- Restrict access to interfaces that allow loading or modifying device tree overlays to privileged users only
Patch Information
The fix was merged across multiple stable kernel branches. Reference the upstream commits: Kernel Git Commit 0b0d570, Kernel Git Commit 4679544, Kernel Git Commit 5d59fd6, Kernel Git Commit 733e627, Kernel Git Commit c7f24b7, Kernel Git Commit cf7385c, Kernel Git Commit e45b693, and Kernel Git Commit ee33202. Distribution-specific guidance is available in the Debian LTS Announcement May 2025 and Debian LTS Announcement October 2025.
Workarounds
- No official upstream workaround exists short of patching; restrict who can supply device tree data to the kernel
- On embedded and virtualized platforms, validate device tree blobs from trusted build pipelines before deployment
- Where feasible, disable runtime device tree overlay loading via kernel configuration on systems that do not require it
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
