CVE-2026-99278: ksmbd: limit sessions on each connection
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: limit sessions on each connection
The pending setup limit only counts InProgress sessions. A client can complete authentication repeatedly and retain an unbounded number of Valid sessions on one connection.
Reserve a connection slot before allocating a session and retain a connection reference while authentication is in progress. The first SMB3 channel takes over that reservation; binding to another connection reserves one slot there. Reauthentication and authentication continuation reuse the existing reservation. Return slots on allocation or insertion failure, channel removal, and final session destruction.
Accept maxsessionsperconnection in reserved startup-request space and default to 64 when older tools leave it zero. Keep the request size and existing field offsets unchanged. Expose the configured limit in procfs. The existing connection limits bound the aggregate number of sessions without a separate global session allocation limit.
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Set max_sessions_per_connection to 64; older tools that leave the setting at zero use a default limit of 64 sessions per connection.
ksmbd max_sessions_per_connection = 64