---
id: CVE-2026-98034
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: Mark NULL kptr stores precise

  check_map_kptr_access() permits a scalar store into an untrusted kptr
  field only when the register is known to contain zero
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: Mark NULL kptr stores precise

  check_map_kptr_access() permits a scalar store into an untrusted kptr
  field only when the register is known to contain zero. Unlike …
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 61df10c7799e27807ad5e459eec9d77cddf8bf45 <
    86168208737bdd267d92d855d453d1d2f840df19
  - >-
    Linux >= 61df10c7799e27807ad5e459eec9d77cddf8bf45 <
    ecdc5043794c9184aa8e6c814603899479c46b35
  - Linux b5a8069835e5236824a84281592d29f859b33153
  - Linux >= 5.18.18 < 5.19
  - Linux 5.19
published: '2026-09-25'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T11:17:32.123'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-98034'
references:
  - url: 'https://git.kernel.org/stable/c/86168208737bdd267d92d855d453d1d2f840df19'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ecdc5043794c9184aa8e6c814603899479c46b35'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-25T11:06:38.852Z'
---

## Overview

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

bpf: Mark NULL kptr stores precise

check_map_kptr_access() permits a scalar store into an untrusted kptr
field only when the register is known to contain zero. Unlike other
verifier checks whose outcome depends on a scalar value, it does not mark
that register precise.

A state checkpoint reached with an imprecise zero can therefore prune a
second path that reaches the store with an arbitrary nonzero scalar. The
program can write attacker-controlled bits into the kptr field and load
them back as a PTR_TO_BTF_ID.

Call mark_chain_precision() before accepting a known-zero register. This
forces state equivalence to compare its scalar range and makes the verifier
visit and reject a path carrying a nonzero value.

## Remediation

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