CVE-2025-38652 in Linux
Summary
by MITRE • 08/22/2025
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to avoid out-of-boundary access in devs.path
- touch /mnt/f2fs/012345678901234567890123456789012345678901234567890123 - truncate -s $((1024*1024*1024)) \ /mnt/f2fs/012345678901234567890123456789012345678901234567890123 - touch /mnt/f2fs/file - truncate -s $((1024*1024*1024)) /mnt/f2fs/file - mkfs.f2fs /mnt/f2fs/012345678901234567890123456789012345678901234567890123 \ -c /mnt/f2fs/file - mount /mnt/f2fs/012345678901234567890123456789012345678901234567890123 \ /mnt/f2fs/loop
[16937.192225] F2FS-fs (loop0): Mount Device [ 0]: /mnt/f2fs/012345678901234567890123456789012345678901234567890123\xff\x01, 511, 0 - 3ffff
[16937.192268] F2FS-fs (loop0): Failed to find devices
If device path length equals to MAX_PATH_LEN, sbi->devs.path[] may
not end up w/ null character due to path array is fully filled, So accidently, fields locate after path[] may be treated as part of
device path, result in parsing wrong device path.
struct f2fs_dev_info {
... char path[MAX_PATH_LEN];
... };
Let's add one byte space for sbi->devs.path[] to store null
character of device path string.
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Analysis
by VulDB Data Team • 05/29/2026
The vulnerability described in CVE-2025-38652 resides within the F2FS (Flash-Friendly File System) implementation in the Linux kernel, specifically concerning how device paths are handled during mount operations. This flaw manifests as an out-of-bounds memory access condition that can lead to system instability or potential exploitation. The issue occurs when the device path length reaches the maximum allowed value defined by MAX_PATH_LEN, which typically corresponds to a fixed buffer size in kernel memory. When this boundary condition is met, the system fails to properly null-terminate the device path string stored in the f2fs_dev_info structure, causing subsequent memory fields to be incorrectly interpreted as part of the device path. This misinterpretation leads to parsing errors and ultimately results in mount failures as demonstrated by the error message "Failed to find devices" during the mounting process.
The technical root cause of this vulnerability lies in the insufficient buffer management within the F2FS subsystem's device information handling code. The f2fs_dev_info structure contains a fixed-size character array path[MAX_PATH_LEN] designed to store device path strings. However, when a device path reaches exactly the maximum length allowed, the code does not account for the necessary null terminator byte required for C-style string handling. This creates a scenario where memory immediately following the path array may contain arbitrary data that gets interpreted as part of the device path string, leading to incorrect device path parsing. This type of vulnerability is classified under CWE-121 as a buffer overflow condition, specifically involving stack-based buffer overflows where insufficient space is allocated for null termination. The improper handling of string boundaries and memory layout creates a condition where adjacent memory fields can be inadvertently included in string processing operations, violating fundamental memory safety principles.
The operational impact of this vulnerability extends beyond simple mount failures to potentially enable more serious security implications within the Linux kernel environment. When the device path parsing fails due to incorrect memory interpretation, the system cannot properly identify or access the intended storage device, leading to complete mount failures and potential data accessibility issues. In environments where F2FS is used for critical storage operations or where automated mounting processes rely on specific device paths, this vulnerability could result in service disruptions or system unavailability. The vulnerability's exploitation potential increases when considering that similar buffer overflows can often be leveraged for privilege escalation or information disclosure attacks, especially when combined with other kernel vulnerabilities. The ATT&CK framework would categorize this as a technique involving kernel memory corruption, potentially enabling privilege escalation through exploitation of memory safety flaws in the file system layer.
Mitigation strategies for CVE-2025-38652 focus on ensuring proper buffer sizing and null termination in the F2FS device path handling code. The recommended fix involves adding one additional byte to the path array within the f2fs_dev_info structure to guarantee sufficient space for the null terminator character. This simple but crucial modification ensures that device path strings are always properly null-terminated regardless of their length, eliminating the possibility of adjacent memory fields being interpreted as part of the device path. System administrators should prioritize applying kernel updates containing this fix, particularly in environments where F2FS is actively used for storage operations. Additionally, monitoring for mount failures or device path parsing errors in system logs can serve as early indicators of potential exploitation attempts. The fix aligns with established secure coding practices that emphasize buffer boundary checking and proper string termination, representing a fundamental defensive measure against buffer overflow vulnerabilities in kernel space. Organizations should also consider implementing automated patch management processes to ensure timely deployment of security fixes across all systems utilizing the affected file system implementation.