# CVE-2026-89544: SUNRPC: fix gssx_dec_option_array error path bugs

> A NULL pointer dereference in the Linux kernel SUNRPC module can cause a system crash when option array decoding fails.

- **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:** 11 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-100656, BELL-CVE-2026-89544, DEBIAN-CVE-2026-89544, GHSA-xwc4-2qqp-pxh3, UBUNTU-CVE-2026-89544

## What is CVE-2026-89544?

CVE-2026-89544 is a high-severity 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:

SUNRPC: fix gssx_dec_option_array error path bugs

Four coupled defects in the gssx XDR option-array decoder make the
error paths unsafe: a NULL deref in the caller, a refcount leak on
the decoded group_info, and a latent use-after-free that the leak
fix would otherwise expose.

gssx_dec_option_array() sets oa->count = 1 before allocating
oa->data.  If that allocation fails, -ENOMEM is returned with
oa->count == 1 and oa->data == NULL.  All other error paths jump
to free_oa: which frees oa->data and NULLs it but also leaves
oa->count == 1.  The caller trusts the count:

    gssp_accept_sec_context_upcall()
      gssx_dec_accept_sec_context()
        gssx_dec_option_array()        /* fails, count=1 data=NULL */
      data = res.options.data[0].value /* NULL deref */

Independently, free_creds: releases the partially decoded svc_cred
with a bare kfree(creds).  gssx_dec_linux_creds() installs a
groups_alloc() result into creds->cr_group_info; that object is
kvmalloc-backed and refcounted, and only put_group_info() reaches
kvfree().  A plain kfree(creds) drops the wrapper and leaks the
group_info allocation.

The natural fix for the leak is to call free_svc_cred(creds) before
kfree(creds), but free_svc_cred() invokes put_group_info() on
creds->cr_group_info unconditionally when non-NULL.  The existing
out_free_groups: path in gssx_dec_linux_creds() already called
groups_free() on that pointer without clearing it, so once
free_svc_cred() is wired in, the subsequent put_group_info() would
touch freed memory.

Fix all four together:

  - Move the oa->count = 1 assignment below the oa->data allocation
    so it is never set when oa->data is NULL.
  - Reset oa->count to 0 at free_oa: so count and data stay
    coherent and the caller sees an empty option array.
  - Call free_svc_cred(creds) before kfree(creds) at free_creds:
    so the refcounted cr_group_info is released.  free_svc_cred()
    either NULL-guards each field explicitly (cr_group_info has
    an if() check) or delegates to a helper that is NULL-safe
    itself (kfree for the string fields, gss_mech_put() which
    guards with if(gm) at gss_mech_switch.c:342), so it is safe
    to call on a partially decoded svc_cred where only
    cr_uid/cr_gid/cr_group_info have been written and everything
    else is zero from kzalloc.
  - In gssx_dec_linux_creds()'s out_free_groups: path, release
    cr_group_info with put_group_info() rather than groups_free()
    so the teardown matches free_svc_cred()'s refcount-aware path,
    and clear the pointer so a later free_svc_cred() on the same
    creds does not release it a second time.

## Which versions are affected by CVE-2026-89544?


## How do I fix CVE-2026-89544?

Apply the vendor's patch.

## Is CVE-2026-89544 being exploited?

There is no known exploitation of CVE-2026-89544 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89544 and fix it if it is affected.

What it is: CVE-2026-89544 is a high-severity 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-2026-89544 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-2026-89544/ (Markdown: https://insights.sbomify.com/CVE-2026-89544/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89544
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89544
- OSV: https://osv.dev/vulnerability/CVE-2026-89544

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89544/
Summaries are generated and may contain mistakes; the official description above is the record.