# CVE-2026-89673: nfsd: fix XDR padding calculation in ff_encode_getdeviceinfo

> A flaw in the Linux kernel NFS server allows remote attackers to read stale memory contents due to incorrect XDR padding calculations.

- **Severity:** Not scored
- **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:** 24 Oct 2026
- **Also known as:** AZL-100091, BELL-CVE-2026-89673, GHSA-fpgc-gpfg-74f9, UBUNTU-CVE-2026-89673

## What is CVE-2026-89673?

CVE-2026-89673 is a 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: fix XDR padding calculation in ff_encode_getdeviceinfo

nfsd4_ff_encode_getdeviceinfo() computes the da_addr_body reservation
as 16 + netid_len + addr_len, but the subsequent xdr_encode_opaque()
calls emit 8 + round_up(netid_len, 4) + round_up(addr_len, 4) bytes.
The mismatch means the declared da_addr_body length exceeds the actual
encoded data by 2-8 bytes on every flexfile GETDEVICEINFO reply,
leaking stale reply-page content to the client and mis-aligning the
subsequent version list decode.

Use xdr_align_size() for each string length to match what
xdr_encode_opaque() actually writes.

## Which versions are affected by CVE-2026-89673?


## How do I fix CVE-2026-89673?

Apply the vendor's patch.

## Is CVE-2026-89673 being exploited?

There is no known exploitation of CVE-2026-89673 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89673 and fix it if it is affected.

What it is: CVE-2026-89673 is a 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-2026-89673 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-2026-89673/ (Markdown: https://insights.sbomify.com/CVE-2026-89673/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89673
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89673
- OSV: https://osv.dev/vulnerability/CVE-2026-89673

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89673/
Summaries are generated and may contain mistakes; the official description above is the record.