CVE-2026-74521
CriticalCVSS 9.1Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
In the Linux kernel's SMB server (ksmbd), a vulnerability was found in the comparison of ClientGUIDs. ClientGUID is a fixed-size binary value and can contain embedded NUL bytes. Using strncmp() stops comparing at the first NUL byte, so different ClientGUID values can incorrectly be treated as equal.
Risk Assessment
The vulnerability could allow unauthorized access or bypass of authentication mechanisms in SMB sessions, posing a threat to data confidentiality and integrity.
Recommendation
Apply the kernel patch that uses memcmp() to compare all SMB2_CLIENT_GUID_SIZE bytes. Update the system to a kernel version containing this fix.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: ksmbd: use memcmp() to compare ClientGUIDs ClientGUID is a fixed-size binary value and can contain embedded NUL bytes. strncmp() stops comparing at the first NUL byte, so different ClientGUID values can incorrectly be treated as equal. Use memcmp() in SMB3 multichannel session binding and FSCTL_VALIDATE_NEGOTIATE_INFO to compare all SMB2_CLIENT_GUID_SIZE bytes.