Executive brief
A vulnerability in the Linux kernel's SMB client could allow sensitive information to be exposed. When debug logging is enabled, the system inadvertently records plaintext usernames and passwords in the system logs. This could allow an attacker with local access to the system logs to steal credentials used for network file sharing.
Technical details
A sensitive information disclosure vulnerability exists in the Linux kernel SMB client component. The function 'cifs_set_cifscreds' in 'fs/smb/client/connect.c' contained a debug statement ('cifs_dbg(FYI, ...)') that printed the entire key payload, including plaintext usernames and passwords, to the kernel log. This occurs when the 'FYI' debug level is enabled. An attacker with local access and the ability to read kernel debug logs (dmesg) could extract these credentials. The vulnerability has been resolved by removing the problematic debug log across multiple stable kernel branches.
Affected products
- Linux Linux kernel 3.3.1 to 5.10.253, 5.11 to 5.15.203, 5.16 to 6.1.167, 6.2 to 6.6.130, 6.7 to 6.12.77, 6.13 to 6.18.17, 6.19 to 6.19.7
Timeline
- 2026-03-25: disclosed: Initial disclosure of the vulnerability
- 2026-03-25: patched: Patches released across various stable kernel versions
References
- https://git.kernel.org/stable/c/2ef0fc3bf49db2b9df36d5f44508c9e384bfa2a1
- https://git.kernel.org/stable/c/2f37dc436d4e61ff7ae0b0353cf91b8c10396e4d
- https://git.kernel.org/stable/c/3990f352bb0adc8688d0949a9c13e3110570eb61
- https://git.kernel.org/stable/c/3e182701db612ddd794ccd5ed822e6cc1db2b972
- https://git.kernel.org/stable/c/54c570de9a35860dfa85fe668f23ddfda8cc7e26
- https://git.kernel.org/stable/c/b746a357abfb8fdb0a171d51ec5091e786d34be1
- https://git.kernel.org/stable/c/e5a3b11e07b335006371915b2da47b6056c9e3bc