# CVE-2026-89544

## Summary

- **CVE ID:** CVE-2026-89544
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** N/A
- **Published:** Sep 11, 2026
- **Last Modified:** Sep 13, 2026

## 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.

## Affected Products

- Linux — Linux (3cfcfc102a5e57b021b786a755a38935e357797d)
- Linux — Linux (b97c37978ca825557d331c9012e0c1ddc0e42364)
- Linux — Linux (bfa9d86d39a0fe4685f90c3529aa9bd62a9d97a8)
- Linux — Linux (bb336cd8d5ecb69c430ebe3e7bcff68471d93fa8)
- Linux — Linux (dd292e884c649f9b1c18af0ec75ca90b390cd044)
- Linux — Linux (934212a623cbab851848b6de377eb476718c3e4c)
- Linux — Linux (5e6013ae2c8d420faea553d363935f65badd32c3)
- Linux — Linux (9806c2393cd2ab0a8e7bb9ffae02ce20e3112ec4)
- Linux — Linux (996997d1fb2126feda550d6adcedcbd94911fc69)
- Linux — Linux (4.19.311)
- Linux — Linux (5.4.273)
- Linux — Linux (5.10.214)
- Linux — Linux (5.15.153)
- Linux — Linux (6.1.83)
- Linux — Linux (6.6.23)
- Linux — Linux (6.7.11)
- Linux — Linux (6.8.2)
- Linux — Linux (6.9)
- Linux — Linux (0)
- Linux — Linux (6.18.51)
- Linux — Linux (7.2.4)
- Linux — Linux (7.3-rc1)

## References

- [CNA](https://git.kernel.org/stable/c/3ff45361e9469e85c0f86b8e7b82c63e50bab8ef)
- [CNA](https://git.kernel.org/stable/c/f85a83774d7f4e2ac71c0c384df0dfb6f7d0179a)
- [CNA](https://git.kernel.org/stable/c/5e9a94539b1ec17a89177d952badfd0d844d694a)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.57%
- **EPSS Percentile:** 45.5

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._