# CVE-2026-53397: nfsd: fix posix_acl leak on SETACL decode failure

> A memory leak in the Linux kernel NFS server allows attackers to exhaust server memory via crafted SETACL requests, causing denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 19 Jul 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-53397, DEBIAN-CVE-2026-53397, GHSA-mpc7-4w3v-v47r, ROOT-OS-DEBIAN-11-CVE-2026-53397, ROOT-OS-UBUNTU-2204-CVE-2026-53397, UBUNTU-CVE-2026-53397

## What is CVE-2026-53397?

CVE-2026-53397 is a high-severity memory corruption vulnerability in Linux kernel, published on 19 Jul 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:

nfsd: fix posix_acl leak on SETACL decode failure

nfsaclsvc_decode_setaclargs() and nfs3svc_decode_setaclargs() each
call nfs_stream_decode_acl() twice, first for NFS_ACL and then for
NFS_DFACL.  Each successful call transfers ownership of a freshly
allocated posix_acl into argp->acl_access or argp->acl_default.  If
the first call succeeds but the second fails, the decoder returns
false and argp->acl_access is left dangling.

ACLPROC2_SETACL.pc_release was wired to nfssvc_release_attrstat and
ACLPROC3_SETACL.pc_release was wired to nfs3svc_release_fhandle.
Both only call fh_put() and have no knowledge of the ACL fields on
argp.  The posix_acl_release() pairs sat at the out: labels inside
nfsacld_proc_setacl() and nfsd3_proc_setacl(), but svc_process()
skips pc_func when pc_decode returns false, so that cleanup is
unreachable on decode failure:

    svc_process_common()
      pc_decode()                  /* decode_setaclargs: false */
      /* pc_func skipped */
      pc_release()                 /* fh_put only -- ACLs leaked */

The orphaned posix_acl is leaked for the lifetime of the server.

Fix by adding nfsaclsvc_release_setacl() and nfs3svc_release_setacl(),
which release both argp->acl_access and argp->acl_default in addition
to fh_put(), and wiring them as pc_release for their respective SETACL
procedures.  pc_release runs on every path svc_process() takes after
decode, including decode failure, so the posix_acl_release() pairs are
removed from the proc functions' out: labels to keep ownership in one
place.  This matches the existing release_getacl() pattern used by
the sibling GETACL procedures.

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

## Which versions are affected by CVE-2026-53397?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53397?

Apply the vendor's patch.

## Is CVE-2026-53397 being exploited?

There is no known exploitation of CVE-2026-53397 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-2026-53397 and fix it if it is affected.

What it is: CVE-2026-53397 is a high-severity memory corruption vulnerability in Linux kernel, published on 19 Jul 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-2026-53397 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-2026-53397/ (Markdown: https://insights.sbomify.com/CVE-2026-53397/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53397
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53397
- OSV: https://osv.dev/vulnerability/CVE-2026-53397

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53397/
Summaries are generated and may contain mistakes; the official description above is the record.