---
id: CVE-2023-40548
title: A buffer overflow was found in Shim in the 32-bit system
summary: >-
  A buffer overflow was found in Shim in the 32-bit system. The overflow happens
  due to an addition operation involving a user-controlled value parsed from the
  PE binary being used by Shim. This value is further used for memory allocation
  …
severity: high
cvss: 7.4
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-190
  - CWE-190
  - CWE-787
vendor: redhat
product: shim
affected:
  - shim < 15.8
  - shim = 15.8
  - fedora = 39
patched:
  - shim 15.8
published: '2024-01-29'
updated: '2026-06-26'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-40548'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2024:1834'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:1835'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:1873'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:1876'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:1883'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:1902'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:1903'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:1959'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:2086'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2023-40548'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2241782'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:1834'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:1835'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:1873'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:1876'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:1883'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:1902'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:1903'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:1959'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/errata/RHSA-2024:2086'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/security/cve/CVE-2023-40548'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2241782'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2024/05/msg00009.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00436
epssPercentile: 0.37351
ingestedAt: '2026-06-26T16:43:13.377Z'
---

## Overview

A buffer overflow was found in Shim in the 32-bit system. The overflow happens due to an addition operation involving a user-controlled value parsed from the PE binary being used by Shim. This value is further used for memory allocation operations, leading to a heap-based buffer overflow. This flaw causes memory corruption and can lead to a crash or data integrity issues during the boot phase.

## Affected

- `shim < 15.8`
- `shim = 15.8`
- `fedora = 39`

## Remediation

Upgrade past the affected range:

- `shim 15.8`