# CVE-2026-72381: ksmbd: fix use-after-free of fp->owner.name in durable handle owner check

> A race condition in the Linux kernel's ksmbd module allows a use-after-free, potentially enabling local attackers to execute code or escalate privileges.

- **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:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72381, DEBIAN-CVE-2026-72381, GHSA-qx34-9c4p-jvq8, UBUNTU-CVE-2026-72381

## What is CVE-2026-72381?

CVE-2026-72381 is a critical use after free vulnerability in Linux, published on 15 Aug 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 of fp->owner.name in durable handle owner check

Two concurrent SMB2 durable reconnects (DH2C/DHnC) on the same
persistent_id race the fp->owner.name compare-read in
ksmbd_vfs_compare_durable_owner() against the kfree() in
ksmbd_reopen_durable_fd()'s reopen-success path. fp->owner.name is a
standalone kstrdup() buffer whose lifetime is independent of the fp
refcount, and the two sites share no lock: the compare reads the buffer
while the reopen frees it, so the strcmp() can dereference freed memory.

Commit 7ce4fc40018d ("ksmbd: fix durable reconnect double-bind race in
ksmbd_reopen_durable_fd") made the fp->conn claim atomic under
global_ft.lock (closing the owner.name double-free and the ksmbd_file
write-UAF), but the compare-read versus reopen-free pair was left
unserialized.

  BUG: KASAN: slab-use-after-free in strcmp+0x2c/0x80
  Read of size 1 by task kworker
    strcmp
    ksmbd_vfs_compare_durable_owner
    smb2_check_durable_oplock
    smb2_open
  Freed by task kworker:
    kfree
    ksmbd_reopen_durable_fd
    smb2_open
  Allocated by task kworker:
    kstrdup
    session_fd_check
    smb2_session_logoff
  The buggy address belongs to the cache kmalloc-8

Serialize both sides of the race with fp->f_lock.  The global durable
file-table lock still protects the durable reconnect claim, but
fp->owner.name is per-open state and does not need to block unrelated
durable table lookups or reconnects.  The teardown is left at its
existing location after the reopen-success point so that an __open_id()
rollback still retains owner.name for a later legitimate reconnect to
verify.

## Which versions are affected by CVE-2026-72381?


## How do I fix CVE-2026-72381?

Apply the vendor's patch.

## Is CVE-2026-72381 being exploited?

There is no known exploitation of CVE-2026-72381 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72381 and fix it if it is affected.

What it is: CVE-2026-72381 is a critical use after free vulnerability in Linux, published on 15 Aug 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-2026-72381 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-2026-72381/ (Markdown: https://insights.sbomify.com/CVE-2026-72381/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72381
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72381
- OSV: https://osv.dev/vulnerability/CVE-2026-72381

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72381/
Summaries are generated and may contain mistakes; the official description above is the record.