---
id: CVE-2026-98132
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO

  states.c:__clean_func_state() can downgrade scalar zero spill to
  STACK_ZERO in the following case:

    *…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO

  states.c:__clean_func_state() can downgrade scalar zero spill to
  STACK_ZERO in the following case:

    *…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= be23266b4a08540aa43d8503a2ea10247c8daebe <
    436fa689630b741a77ef8c4a6f426479affd5bac
  - >-
    Linux >= be23266b4a08540aa43d8503a2ea10247c8daebe <
    2f3536bff8823d3c5fdbbe15e17bfca696cc2b2e
  - Linux 7.1
published: '2026-09-25'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T11:17:44.603'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-98132'
references:
  - url: 'https://git.kernel.org/stable/c/2f3536bff8823d3c5fdbbe15e17bfca696cc2b2e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/436fa689630b741a77ef8c4a6f426479affd5bac'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-25T11:06:38.813Z'
epss: 0.00156
epssPercentile: 0.04036
---

## Overview

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

bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO

states.c:__clean_func_state() can downgrade scalar zero spill to
STACK_ZERO in the following case:

  *(u64 *)(r10 - 8) = 0;
  ... checkpoint ...
  r1 = *(u32 *)(r10 - 4);
  ... no reads from r10-8 ...

Here 4 bytes at r10-8 are dead and verifier changes scalar spill to a
combination: 0000pppp (p stands for poison). Such a change breaks
precision propagation chains. All places that produce STACK_ZERO
should call bpf_mark_chain_precision() for the zero source.

This patch fixes the bug in a simplest way possible:
avoids converting stack spills of zero to STACK_ZERO.
Two smarter approaches are possible:
- do bpf_mark_chain_precision() from __clean_func_state()
- check slot liveness information in check_stack_write_fixed_off()

I investigated both and the changes required are a bit tricky,
hence go with a simple fix for the time being.

## Remediation

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