# CVE-2026-80926: ksmbd: fix use-after-free in oplock break notification

> An authenticated attacker can trigger a use-after-free in the ksmbd SMB server, potentially leading to code execution or privilege escalation.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100751, BELL-CVE-2026-80926, DEBIAN-CVE-2026-80926, GHSA-4r76-cqqc-v36j, UBUNTU-CVE-2026-80926

## What is CVE-2026-80926?

CVE-2026-80926 is a critical use after free vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix use-after-free in oplock break notification

smb2_oplock_break_noti() reads opinfo->conn without any lock and
dereferences it after two allocations which may sleep.  When the
durable handle owning the oplock is disconnected, session_fd_check()
clears opinfo->conn and drops its conn reference under ci->m_lock, and
the last ksmbd_conn_put() frees the connection.  A break triggered by
another connection that races with the teardown can then resurrect the
freed connection: ksmbd_conn_get() is a plain atomic_inc, and the
queued break work later dereferences the stale conn via
ksmbd_conn_write(), a use-after-free reachable by any authenticated
client holding a durable batch oplock.

Thread the caller's inode into the notification path instead of taking
a new reference on it.  Every caller of oplock_break() already holds a
live ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference,
in the parent lease break paths) on the inode that owns the break
target's oplock list, so ci cannot be freed during the call, and its
lock can be taken without dereferencing opinfo->o_fp, which a
concurrent close may free.  Select and pin the connection under
ci->m_lock, the same lock session_fd_check() and
ksmbd_reopen_durable_fd() use to update opinfo->conn, so a concurrent
detach either loses the race to the clear or keeps the connection
alive until the notification work releases it.  Transfer the reference
to the work item and release it on allocation failures.

## Which versions are affected by CVE-2026-80926?


## How do I fix CVE-2026-80926?

Apply the vendor's patch.

## Is CVE-2026-80926 being exploited?

There is no known exploitation of CVE-2026-80926 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80926 and fix it if it is affected.

What it is: CVE-2026-80926 is a critical use after free vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-80926 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-2026-80926/ (Markdown: https://insights.sbomify.com/CVE-2026-80926/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80926
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80926
- OSV: https://osv.dev/vulnerability/CVE-2026-80926

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80926/
Summaries are generated and may contain mistakes; the official description above is the record.