CVE-2026-31392

A flaw was found in the Linux kernel's Server Message Block (SMB) client. A local attacker, by attempting to mount SMB shares using Kerberos (sec=krb5) with a specified username, could cause the client to incorrectly reuse an existing SMB session. This session reuse occurs even when a different username is provided for subsequent mounts, potentially leading to an authentication bypass where shares are accessed with unintended credentials.

This is an authentication bypass vulnerability where SMB shares may be accessed with incorrect credentials due to improper session matching. A local user performing multiple Kerberos-authenticated SMB mounts with different usernames may inadvertently access shares using credentials from a previous mount. This could lead to unauthorized access to network resources.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.