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Fencer Vulns
high 8.3

CVE-2023-40547 json

Shim: rce in http boot support may lead to secure boot bypass

published 2024-01-25 2 y ago modified 2026-06-26 4 mo ago also EUVD-2023-45118

cvss
8.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
5.4%
EPSS 5.4% chance of exploitation in 30 days, percentile 92%
public exploits
0
none known

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 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.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 7 0:15.8-1.el7, 0:15.8-3.el7
  • Red Hat Red Hat Enterprise Linux 8 0:15.8-4.el8_9
  • Red Hat Red Hat Enterprise Linux 8.2 Advanced Update Support 0:15.8-2.el8_2
  • Red Hat Red Hat Enterprise Linux 8.2 Telecommunications Update Service 0:15.8-2.el8_2
  • Red Hat Red Hat Enterprise Linux 8.2 Update Services for SAP Solutions 0:15.8-2.el8_2
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 0:15.8-2.el8_4
  • Red Hat Red Hat Enterprise Linux 8.4 Telecommunications Update Service 0:15.8-2.el8_4
  • Red Hat Red Hat Enterprise Linux 8.4 Update Services for SAP Solutions 0:15.8-2.el8_4
  • Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support 0:15.8-2.el8_6
  • Red Hat Red Hat Enterprise Linux 8.8 Extended Update Support 0:15.8-2.el8
  • Red Hat Red Hat Enterprise Linux 9 0:15.8-4.el9_3
  • Red Hat Red Hat Enterprise Linux 9.0 Extended Update Support 0:15.8-2.el9, 0:15.8-3.el9
  • Red Hat Red Hat Enterprise Linux 9.2 Extended Update Support 0:15.8-3.el9_2
  • shim Debian 12 15.8-1~deb12u1
  • shim Debian 14, Debian 13 15.8-1

debian advisories DEBIAN-CVE-2023-40547

  • shim Ubuntu 24.04 LTS, Ubuntu 22.04 LTS, Ubuntu 20.04 LTS 15.8-0ubuntu1
  • shim-signed Ubuntu 20.04 LTS 1.40.10
  • shim-signed Ubuntu 22.04 LTS 1.51.4
  • shim-signed Ubuntu 24.04 LTS 1.58

ubuntu advisories UBUNTU-CVE-2023-40547

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • shim RHEL 7 15.8-3.el7
  • mokutil RHEL 7 15.8-1.el7
  • shim-x64 RHEL 7 15.8-1.el7
  • shim-ia32 RHEL 7 15.8-1.el7
  • shim-signed RHEL 7 15.8-1.el7
  • shim-unsigned-x64 RHEL 7 15.8-3.el7
  • shim-unsigned-ia32 RHEL 7 15.8-3.el7
  • shim RHEL 9 15.8-4.el9_3

red hat advisories RHSA-2024:2086RHSA-2024:1959RHSA-2024:1903RHSA-2024:1902RHSA-2024:1873RHSA-2024:1876

  • shim Linux Micro 6.0 15.8-1.1
  • pcr-oracle Linux Micro 6.0 0.4.6-2.1
  • shim SLES for SAP 12 SP5, SLES 12 SP5 15.8-25.30.1
  • shim SLES for SAP 15 SP4, SLES for SAP 15 SP3, SLES 15 SP4-LTSS +16 more 15.8-150300.4.20.2
  • shim SLES for SAP 15 SP2, SLES 15 SP2-LTSS, SLE High Performance Computing 15 SP2-LTSS 15.8-150100.3.38.1

suse advisories SUSE-SU-2025:20136-1SUSE-SU-2024:1462-1SUSE-SU-2024:1461-1SUSE-SU-2024:1368-1

  • shim-x64 AlmaLinux 8 15.8-4.el8_9.alma.1
  • shim-aa64 AlmaLinux 8 15.8-4.el8_9.alma.1
  • shim-ia32 AlmaLinux 8 15.8-4.el8_9.alma.1
  • shim-x64 AlmaLinux 9 15.8-4.el9_3.alma.1
  • shim-aa64 AlmaLinux 9 15.8-4.el9_3.alma.1

almalinux advisories ALSA-2024:1902ALSA-2024:1903

  • shim-unsigned-x64 CBL-Mariner 2.0 15.8-1
  • shim CBL-Mariner 2.0 15.8-1
  • shim Azure Linux 3.0 15.8-3
  • shim-unsigned-aarch64 Azure Linux 3.0 15.8-3
  • shim-unsigned-x64 Azure Linux 3.0 15.8-3

azure linux advisories AZL-33895AZL-34030AZL-35254AZL-35267AZL-35278

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2023-40547 updated cvss 8.3

shim: RCE in http boot support may lead to Secure Boot bypass

  • Red Hat CodeReady Linux Builder EUS (v.8.8) shim-unsigned-x64 15.8-2.el8
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1883
  • Red Hat CodeReady Linux Builder EUS (v.9.0) shim-unsigned-x64 15.8-2.el9 Red Hat Enterprise Linux AppStream EUS (v.9.0) shim-unsigned-aarch64 15.8-2.el9
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1835
  • Red Hat Enterprise Linux BaseOS (v. 8) shim 15.8-4.el8_9, shim-x64 15.8-4.el8_9, shim-aa64 15.8-4.el8_9, shim-ia32 15.8-4.el8_9
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1902
  • Red Hat Enterprise Linux BaseOS (v. 9) shim 15.8-4.el9_3, shim-x64 15.8-4.el9_3, shim-aa64 15.8-4.el9_3
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1903
  • Red Hat Enterprise Linux BaseOS AUS (v. 8.2) shim 15.8-2.el8_2, shim-x64 15.8-2.el8_2, shim-ia32 15.8-2.el8_2
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1834
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4) shim 15.8-2.el8_4, shim-x64 15.8-2.el8_4, shim-ia32 15.8-2.el8_4
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1873
  • Red Hat Enterprise Linux BaseOS E4S (v. 8.2) shim 15.8-2.el8_2, shim-x64 15.8-2.el8_2, shim-ia32 15.8-2.el8_2
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1834
  • Red Hat Enterprise Linux BaseOS E4S (v.8.4) shim 15.8-2.el8_4, shim-x64 15.8-2.el8_4, shim-ia32 15.8-2.el8_4
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1873
show 7 more
  • Red Hat Enterprise Linux BaseOS EUS (v.8.6) shim 15.8-2.el8_6, shim-x64 15.8-2.el8_6, shim-aa64 15.8-2.el8_6, shim-ia32 15.8-2.el8_6
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:2086
  • Red Hat Enterprise Linux BaseOS EUS (v.8.8) shim 15.8-2.el8, shim-x64 15.8-2.el8, shim-aa64 15.8-2.el8, shim-ia32 15.8-2.el8
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1883
  • Red Hat Enterprise Linux BaseOS EUS (v.9.0) shim 15.8-3.el9, shim-x64 15.8-3.el9, shim-aa64 15.8-3.el9
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1835
  • Red Hat Enterprise Linux BaseOS EUS (v.9.2) shim 15.8-3.el9_2, shim-x64 15.8-3.el9_2, shim-aa64 15.8-3.el9_2
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1876
  • Red Hat Enterprise Linux BaseOS TUS (v. 8.2) shim 15.8-2.el8_2, shim-x64 15.8-2.el8_2, shim-ia32 15.8-2.el8_2
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1834
  • Red Hat Enterprise Linux BaseOS TUS (v.8.4) shim 15.8-2.el8_4, shim-x64 15.8-2.el8_4, shim-ia32 15.8-2.el8_4
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1873
  • Red Hat Enterprise Linux Client (v. 7) shim 15.8-3.el7, mokutil 15.8-1.el7, shim-x64 15.8-1.el7, shim-ia32 15.8-1.el7, shim-signed 15.8-1.el7, shim-unsigned-x64 15.8-3.el7, +1 more Red Hat Enterprise Linux Server (v. 7) shim 15.8-3.el7, mokutil 15.8-1.el7, shim-x64 15.8-1.el7, shim-ia32 15.8-1.el7, shim-signed 15.8-1.el7, shim-unsigned-x64 15.8-3.el7, +1 more Red Hat Enterprise Linux Workstation (v. 7) shim 15.8-3.el7, mokutil 15.8-1.el7, shim-x64 15.8-1.el7, shim-ia32 15.8-1.el7, shim-signed 15.8-1.el7, shim-unsigned-x64 15.8-3.el7, +1 more
    fixed: vendor fix “If a system isn’t required to boot from the network, configure the server’s boot order to disable entirely or skip the network boot.” RHSA-2024:1959

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2 y ago

Exploit prediction

5.42% chance of exploitation in the next 30 days, higher than 92% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.3 CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 8.3 CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected products

  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 8.2 Advanced Update Support
  • Red Hat Red Hat Enterprise Linux 8.2 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.2 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.4 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.4 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 8.8 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Enterprise Linux 9.0 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 9.2 Extended Update Support

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.