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


- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 23 Oct 2026
- **Updated:** 24 Oct 2026
- **Also known as:** GHSA-wr5r-399q-pwfr, UBUNTU-CVE-2026-98870

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98870 and fix it if it is affected.

What it is: CVE-2026-98870 is a high-severity vulnerability in Linux, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-98870 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98870/ (Markdown: https://insights.sbomify.com/CVE-2026-98870/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98870
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98870
- OSV: https://osv.dev/vulnerability/CVE-2026-98870

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98870/
Summaries are generated and may contain mistakes; the official description above is the record.