CVE-2025-38692 in Linux
Summary
by MITRE • 09/04/2025
In the Linux kernel, the following vulnerability has been resolved:
exfat: add cluster chain loop check for dir
An infinite loop may occur if the following conditions occur due to file system corruption.
(1) Condition for exfat_count_dir_entries() to loop infinitely. - The cluster chain includes a loop. - There is no UNUSED entry in the cluster chain.
(2) Condition for exfat_create_upcase_table() to loop infinitely. - The cluster chain of the root directory includes a loop. - There are no UNUSED entry and up-case table entry in the cluster chain of the root directory.
(3) Condition for exfat_load_bitmap() to loop infinitely. - The cluster chain of the root directory includes a loop. - There are no UNUSED entry and bitmap entry in the cluster chain of the root directory.
(4) Condition for exfat_find_dir_entry() to loop infinitely. - The cluster chain includes a loop. - The unused directory entries were exhausted by some operation.
(5) Condition for exfat_check_dir_empty() to loop infinitely. - The cluster chain includes a loop. - The unused directory entries were exhausted by some operation. - All files and sub-directories under the directory are deleted.
This commit adds checks to break the above infinite loop.
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Analysis
by VulDB Data Team • 02/10/2026
The vulnerability described in CVE-2025-38692 represents a critical flaw in the Linux kernel's exFAT file system implementation that can lead to denial of service through infinite loop conditions. This issue specifically affects systems utilizing the exFAT file system where file system corruption has occurred, creating circular references within cluster chains that cause kernel functions to enter indefinite loops. The vulnerability manifests when the kernel attempts to process directory entries in corrupted exFAT file systems, where cluster chains contain loops that prevent normal traversal operations from completing. These infinite loops can exhaust system resources and render the affected system unresponsive, making this a significant security concern for any Linux system running exFAT file systems.
The technical flaw stems from insufficient validation of cluster chain integrity within the exFAT driver implementation. When the kernel encounters corrupted file system structures, functions such as exfat_count_dir_entries, exfat_create_upcase_table, exfat_load_bitmap, exfat_find_dir_entry, and exfat_check_dir_empty fail to properly detect circular references in cluster chains. The conditions for exploitation require specific combinations of file system corruption patterns where looped cluster chains lack proper termination markers such as UNUSED entries. This design flaw allows attackers who can manipulate or corrupt exFAT file systems to trigger these infinite loops through normal file system operations, effectively creating a denial of service condition that can be exploited remotely or locally depending on system configuration.
The operational impact of this vulnerability extends beyond simple system unresponsiveness to potentially compromise entire system availability. When any of the affected functions enter infinite loops, they consume excessive CPU cycles and memory resources, leading to system instability and potential crashes. The vulnerability affects multiple kernel functions that process directory structures, meaning that various file system operations can trigger the condition, making it difficult to predict or prevent. Systems using exFAT file systems, particularly those in server environments or embedded systems where continuous operation is critical, face significant risk from this flaw. The vulnerability can be particularly dangerous in automated environments where file system corruption might occur due to hardware failures, power loss during write operations, or malicious file system manipulation.
Mitigation strategies for CVE-2025-38692 primarily involve applying the kernel patches that implement loop detection mechanisms in the exFAT driver. The fix introduces checks that identify and break infinite loops in cluster chain traversal operations, preventing the kernel from entering indefinite loops when encountering corrupted file system structures. System administrators should prioritize updating their Linux kernels to versions containing the patched exFAT implementation, particularly in production environments where exFAT file systems are in use. Additionally, implementing robust file system monitoring and backup strategies can help detect corruption before it leads to exploitation, while regular file system checks and integrity validation can prevent the accumulation of corrupted structures that might trigger these conditions. Organizations should also consider implementing automated alerts for file system errors and ensure proper power management to prevent corruption from occurring in the first place, as this vulnerability specifically targets scenarios involving file system corruption rather than direct exploitation. The fix aligns with security best practices for preventing denial of service attacks through resource exhaustion and demonstrates the importance of proper input validation in kernel space file system drivers.
This vulnerability maps to CWE-835 (Loop with Unreachable Exit Condition) and relates to ATT&CK technique T1499.001 (Network Denial of Service) through the potential for remote exploitation. The implementation of proper loop detection and early termination conditions in the kernel file system driver represents a fundamental security measure that prevents resource exhaustion attacks and ensures system stability. The fix addresses a core design flaw in the exFAT driver's cluster chain traversal logic, which is consistent with the principles of secure coding practices that emphasize defensive programming and input validation.