CVE-2026-98870 ksmbd: remove stale channels from all sessions on teardown
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-98870?
CVE-2026-98870 is a high-severity vulnerability in Linux, published on 23 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: remove stale channels from all sessions on teardown
ksmbd_sessions_deregister() removes a connection's channels from other sessions' channel lists only while conn->binding is still set:
if (conn->binding) { hash_for_each_safe(sessions_table, ...) ksmbd_chann_del(conn, sess); }
conn->binding is a transient flag: it is cleared once a binding SESSION_SETUP completes, and also by a subsequent non-binding SESSION_SETUP on the same connection (a reauthentication on a bound channel, or a new SessionId==0 setup). A connection that has bound a channel into another session's ksmbd_chann_list and then clears conn->binding leaves that channel behind when it disconnects: the channel, whose chann->conn points at the now freed struct ksmbd_conn, stays on the owner session's list.
When the owning connection later tears down, the second loop dereferences the stale channel:
xa_for_each(&sess->ksmbd_chann_list, chann_id, chann) if (chann->conn != conn) ksmbd_conn_set_exiting(chann->conn); /* freed */
which is a use-after-free write into the freed ksmbd_conn (the same stale channel is also walked by show_proc_session() through /proc). The session is leaked as well, because its channel list never empties.
Remove the conn->binding gate so a connection always removes its channels from every session on teardown.
Which versions are affected by CVE-2026-98870?
How do I fix CVE-2026-98870?
No fix has been published for CVE-2026-98870 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-98870 being exploited?
There is no known exploitation of CVE-2026-98870 in the wild and no public exploit code.
Sources
Also known as GHSA-wr5r-399q-pwfr, UBUNTU-CVE-2026-98870.