# CVE-2025-22070: fs/9p: fix NULL pointer dereference on mkdir

> A local attacker can crash the Linux kernel by creating a directory on a 9p filesystem mounted with POSIX ACLs enabled.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Apr 2025
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-61700, BELL-CVE-2025-22070, DEBIAN-CVE-2025-22070, GHSA-jprx-mprp-6qvx, ROOT-OS-DEBIAN-12-CVE-2025-22070, ROOT-OS-UBUNTU-2404-CVE-2025-22070, UBUNTU-CVE-2025-22070

## What is CVE-2025-22070?

CVE-2025-22070 is a medium-severity vulnerability in Linux kernel, published on 16 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

fs/9p: fix NULL pointer dereference on mkdir

When a 9p tree was mounted with option 'posixacl', parent directory had a
default ACL set for its subdirectories, e.g.:

  setfacl -m default:group:simpsons:rwx parentdir

then creating a subdirectory crashed 9p client, as v9fs_fid_add() call in
function v9fs_vfs_mkdir_dotl() sets the passed 'fid' pointer to NULL
(since dafbe689736) even though the subsequent v9fs_set_create_acl() call
expects a valid non-NULL 'fid' pointer:

  [   37.273191] BUG: kernel NULL pointer dereference, address: 0000000000000000
  ...
  [   37.322338] Call Trace:
  [   37.323043]  <TASK>
  [   37.323621] ? __die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434)
  [   37.324448] ? page_fault_oops (arch/x86/mm/fault.c:714)
  [   37.325532] ? search_module_extables (kernel/module/main.c:3733)
  [   37.326742] ? p9_client_walk (net/9p/client.c:1165) 9pnet
  [   37.328006] ? search_bpf_extables (kernel/bpf/core.c:804)
  [   37.329142] ? exc_page_fault (./arch/x86/include/asm/paravirt.h:686 arch/x86/mm/fault.c:1488 arch/x86/mm/fault.c:1538)
  [   37.330196] ? asm_exc_page_fault (./arch/x86/include/asm/idtentry.h:574)
  [   37.331330] ? p9_client_walk (net/9p/client.c:1165) 9pnet
  [   37.332562] ? v9fs_fid_xattr_get (fs/9p/xattr.c:30) 9p
  [   37.333824] v9fs_fid_xattr_set (fs/9p/fid.h:23 fs/9p/xattr.c:121) 9p
  [   37.335077] v9fs_set_acl (fs/9p/acl.c:276) 9p
  [   37.336112] v9fs_set_create_acl (fs/9p/acl.c:307) 9p
  [   37.337326] v9fs_vfs_mkdir_dotl (fs/9p/vfs_inode_dotl.c:411) 9p
  [   37.338590] vfs_mkdir (fs/namei.c:4313)
  [   37.339535] do_mkdirat (fs/namei.c:4336)
  [   37.340465] __x64_sys_mkdir (fs/namei.c:4354)
  [   37.341455] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)
  [   37.342447] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

Fix this by simply swapping the sequence of these two calls in
v9fs_vfs_mkdir_dotl(), i.e. calling v9fs_set_create_acl() before
v9fs_fid_add().

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2025-22070?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-22070?

Apply the vendor's patch.

## Is CVE-2025-22070 being exploited?

There is no known exploitation of CVE-2025-22070 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-22070 and fix it if it is affected.

What it is: CVE-2025-22070 is a medium-severity vulnerability in Linux kernel, published on 16 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-22070 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2025-22070/ (Markdown: https://insights.sbomify.com/CVE-2025-22070/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-22070
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-22070
- OSV: https://osv.dev/vulnerability/CVE-2025-22070

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-22070/
Summaries are generated and may contain mistakes; the official description above is the record.