---
id: CVE-2026-93127
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: Drop scalar id on sign-extending narrowing stack fills

  When a spilled scalar is filled back with a sign-extending narrowing load
  (BPF_MEMSX), check_stack_read_fix…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: Drop scalar id on sign-extending narrowing stack fills

  When a spilled scalar is filled back with a sign-extending narrowing load
  (BPF_MEMSX), check_stack_read_fix…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 3cd5c890652ba1f0682adc291b5446245259b692 <
    f3614622dc41f3dd99bb4f691da253814e4e6cae
  - >-
    Linux >= 3cd5c890652ba1f0682adc291b5446245259b692 <
    2cb5f4ca695ebe552647e5ba4aad6934d6a43bae
  - Linux 7.0
published: '2026-09-17'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T18:18:22.070'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93127'
references:
  - url: 'https://git.kernel.org/stable/c/2cb5f4ca695ebe552647e5ba4aad6934d6a43bae'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f3614622dc41f3dd99bb4f691da253814e4e6cae'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
epss: 0.00165
epssPercentile: 0.05028
ingestedAt: '2026-09-17T16:21:47.749Z'
---

## Overview

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

bpf: Drop scalar id on sign-extending narrowing stack fills

When a spilled scalar is filled back with a sign-extending narrowing load
(BPF_MEMSX), check_stack_read_fixed_off() copies the spilled register
including its scalar id, but coerce_reg_to_size_sx() then sign-extends the
filled register's value. If the same slot is also filled with a plain
zero-extending load (BPF_MEM), both destination registers share the id yet
hold different values. A later 'if <zext-reg> == const' then refines the
sign-extended register through sync_linked_regs() to a value it does not
have at runtime (e.g. the verifier believes 0x80000000 while the register
is 0xffffffff80000000), which can be turned into an out-of-bounds access.

Drop the shared scalar id at the sign-extension site in check_mem_access()
when sign extension actually changes the value, mirroring the BPF_MOVSX
handling in check_alu_op() (no_sext = reg_umax < 2^(size*8-1)).

## Remediation

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