---
id: CVE-2023-40547
title: A remote code execution vulnerability was found in Shim
summary: >-
  A remote code execution vulnerability was found in Shim. The Shim boot support
  trusts attacker-controlled values when parsing an HTTP response. This flaw
  allows an attacker to craft a specific malicious HTTP request, leading to a
  complet…
severity: high
cvss: 8.3
cvssVector: 'CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H'
cwe:
  - CWE-787
  - CWE-346
  - CWE-787
vendor: redhat
product: shim
affected:
  - shim < 15.8
  - enterprise_linux = 7.0
  - enterprise_linux = 8.0
  - enterprise_linux = 9.0
patched:
  - shim 15.8
published: '2024-01-25'
updated: '2026-06-26'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-40547'
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-2023-40547'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2234589'
    label: secalert@redhat.com
  - url: 'http://www.openwall.com/lists/oss-security/2024/01/26/1'
    label: af854a3a-2127-422b-91ae-364da2661108
  - 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-2023-40547'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2234589'
    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: 0.05417
epssPercentile: 0.92398
ingestedAt: '2026-06-26T16:43:13.375Z'
---

## Overview

A remote code execution vulnerability was found in Shim. The Shim boot support trusts attacker-controlled values when parsing an HTTP response. This flaw allows an attacker to craft a specific malicious HTTP request, leading to a completely controlled out-of-bounds write primitive and complete system compromise. This flaw is only exploitable during the early boot phase, an attacker needs to perform a Man-in-the-Middle or compromise the boot server to be able to exploit this vulnerability successfully.

## Affected

- `shim < 15.8`
- `enterprise_linux = 7.0`
- `enterprise_linux = 8.0`
- `enterprise_linux = 9.0`

## Remediation

Upgrade past the affected range:

- `shim 15.8`