---
id: CVE-2026-98038
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: Keep refcount_acquire nullable for borrowed RCU kptrs

  bpf_refcount_acquire() is fallible for a borrowed reference because the
  object may have reached a zero refco…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: Keep refcount_acquire nullable for borrowed RCU kptrs

  bpf_refcount_acquire() is fallible for a borrowed reference because the
  object may have reached a zero refco…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1b12171533a9bb23cf6fba7262b479028b65e1e8 <
    85074498228a2500ea8b8039c49cc1ab8ad5328f
  - >-
    Linux >= 1b12171533a9bb23cf6fba7262b479028b65e1e8 <
    dc36739e5cc9f60485418a910b42bc95339218d2
  - Linux 6.8
published: '2026-09-25'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T11:17:32.560'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-98038'
references:
  - url: 'https://git.kernel.org/stable/c/85074498228a2500ea8b8039c49cc1ab8ad5328f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/dc36739e5cc9f60485418a910b42bc95339218d2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-25T11:06:38.851Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

bpf: Keep refcount_acquire nullable for borrowed RCU kptrs

bpf_refcount_acquire() is fallible for a borrowed reference because the
object may have reached a zero refcount. The verifier therefore keeps
KF_RET_NULL on the return value unless the argument is an owning reference.

An RCU-protected load of a local kptr is marked MEM_ALLOC, but it only
receives NON_OWN_REF when the pointee contains a graph node. A refcounted
object without a graph node consequently looks like an owning reference
even though the loaded register has no acquired reference state. If the
program drops the last real reference while remaining in the RCU critical
section, refcount_inc_not_zero() returns NULL while the verifier treats the
result as non-NULL.

Only classify the argument as owning when it is backed by a verifier-tracked
reference. This retains the non-NULL return for pointers from bpf_obj_new(),
bpf_kptr_xchg(), or an earlier successful acquisition, while requiring a
NULL check for borrowed RCU kptrs.

[ kkd: Rewrote commit log ]

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.