# CVE-2026-89672: nfsd: gate nfs2 setacl by argp->mask

> An attacker can silently delete directory default ACLs via NFSv2 SETACL requests due to missing mask validation in the Linux kernel.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **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-100368, BELL-CVE-2026-89672, DEBIAN-CVE-2026-89672, GHSA-cpgj-m749-r929, UBUNTU-CVE-2026-89672

## What is CVE-2026-89672?

CVE-2026-89672 is a critical missing authorization 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:

nfsd: gate nfs2 setacl by argp->mask

The NFSACL v2 SETACL path shares the decoder convention used by its
v3 sibling: nfsaclsvc_decode_setaclargs() fills in argp->acl_access
only when NFS_ACL is set in the request mask and argp->acl_default
only when NFS_DFACL is set, leaving the other pointer NULL because
the argument buffer is zeroed up to pc_argzero before decode.

nfsacld_proc_setacl() then hands both pointers to set_posix_acl()
unconditionally. set_posix_acl(idmap, dentry, type, NULL) is the VFS
"remove this ACL type" operation, so an omitted arm is
indistinguishable from an explicit request to delete that ACL. A
SETACL carrying only NFS_ACL silently strips the directory's default
ACL; mask=0 strips both.

This is the same defect just fixed in nfsd3_proc_setacl(); apply the
same remedy. Gate each set_posix_acl() call on its mask bit and
initialize error to 0 so that a request with neither bit set leaves
the on-disk ACLs untouched and returns success. The out_drop_lock
path and the unconditional posix_acl_release() in
nfsaclsvc_release_setacl() already tolerate the skipped arms.

## Which versions are affected by CVE-2026-89672?


## How do I fix CVE-2026-89672?

Apply the vendor's patch.

## Is CVE-2026-89672 being exploited?

There is no known exploitation of CVE-2026-89672 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89672 and fix it if it is affected.

What it is: CVE-2026-89672 is a critical missing authorization 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-2026-89672 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-2026-89672/ (Markdown: https://insights.sbomify.com/CVE-2026-89672/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89672
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89672
- OSV: https://osv.dev/vulnerability/CVE-2026-89672

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89672/
Summaries are generated and may contain mistakes; the official description above is the record.