# CVE-2026-53396: nfsd: fix posix_acl leak and ignored error in nfsd4_create_file

> A memory leak in the Linux kernel NFS server allows remote attackers to cause denial of service by triggering repeated file creation failures with invalid ACLs.

- **Severity:** High 7.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-53396, GHSA-x7f6-m4r7-q3h7, UBUNTU-CVE-2026-53396

## What is CVE-2026-53396?

CVE-2026-53396 is a high-severity memory corruption vulnerability in Linux kernel, published on 19 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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

nfsd: fix posix_acl leak and ignored error in nfsd4_create_file

nfsd4_create_file() has two bugs in its ACL handling:

The return value of nfsd4_acl_to_attr() is silently discarded.  When
the NFSv4-to-POSIX ACL conversion fails (e.g., -EINVAL for
unsupported ACE types), the file is created without any ACL and the
client receives NFS4_OK.  This violates RFC 7530/8881 which require
the server to reject unsupported attributes on CREATE.

When start_creating() fails after ACL attributes have been populated
in attrs (either via nfsd4_acl_to_attr or via ownership transfer from
open->op_dpacl/op_pacl), the function jumps to out_write which skips
nfsd_attrs_free().  The posix_acl allocations are leaked.  A client
can trigger this repeatedly with OPEN(CREATE), ACL attributes, and an
invalid filename (e.g., longer than NAME_MAX).

Fix both by capturing the nfsd4_acl_to_attr() return value and by
changing the early error paths to jump to out instead of out_write.
Initialize child to ERR_PTR(-EINVAL) so that end_creating() is safe
to call even if start_creating() was never reached.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-53396?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53396?

Apply the vendor's patch.

## Is CVE-2026-53396 being exploited?

There is no known exploitation of CVE-2026-53396 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-2026-53396 and fix it if it is affected.

What it is: CVE-2026-53396 is a high-severity memory corruption vulnerability in Linux kernel, published on 19 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-53396 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-2026-53396/ (Markdown: https://insights.sbomify.com/CVE-2026-53396/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53396
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53396
- OSV: https://osv.dev/vulnerability/CVE-2026-53396

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53396/
Summaries are generated and may contain mistakes; the official description above is the record.