CVE-2025-39942: 
CBL Mariner vulnerability analysis and mitigation

CVE-2025-39942 is a vulnerability discovered in the Linux kernel, specifically affecting the ksmbd SMBDirect implementation. The vulnerability was disclosed on October 4, 2025, and involves improper validation of remaining_data_length against max_fragmented_recv_size in the SMBDirect protocol handling (NVD, RedHat).

The vulnerability relates to the verification of remaining_data_length in relation to max_fragmented_recv_size within the ksmbd SMBDirect implementation. This issue was inspired by similar checks for data_offset + data_length validation. The vulnerability has been assigned a CVSS v3.1 base score with the vector AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, indicating a score of 5.5 (RedHat).

Based on the CVSS scoring, the vulnerability has potential impact on system availability (High), while maintaining no direct impact on confidentiality or integrity. The local attack vector and low complexity suggest that exploitation could lead to system resource exhaustion or denial of service conditions (RedHat).

The vulnerability has been resolved in the Linux kernel through patches. Multiple Ubuntu releases including 25.04 plucky, 24.04 LTS noble, and 22.04 LTS jammy have been marked as vulnerable and require updates (Ubuntu).