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CVE-2023-40547

high

Description

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.

References

https://access.redhat.com/errata/RHSA-2024:2086

https://access.redhat.com/errata/RHSA-2024:1959

https://access.redhat.com/errata/RHSA-2024:1903

https://access.redhat.com/errata/RHSA-2024:1902

https://access.redhat.com/errata/RHSA-2024:1883

https://access.redhat.com/errata/RHSA-2024:1876

https://access.redhat.com/errata/RHSA-2024:1873

https://access.redhat.com/errata/RHSA-2024:1835

https://access.redhat.com/errata/RHSA-2024:1834

https://securityaffairs.com/158792/hacking/critical-shim-bug-linux.html?web_view=true

https://eclypsium.com/blog/the-real-shim-shady-how-cve-2023-40547-impacts-most-linux-systems/

https://lists.debian.org/debian-lts-announce/2024/05/msg00009.html

https://bugzilla.redhat.com/show_bug.cgi?id=2234589

https://access.redhat.com/security/cve/CVE-2023-40547

http://www.openwall.com/lists/oss-security/2024/01/26/1

Details

Source: Mitre, NVD

Published: 2024-01-25

Updated: 2026-06-26

Named Vulnerability: Shim Shady

Risk Information

CVSS v2

Base Score: 6.8

Vector: CVSS2#AV:A/AC:H/Au:N/C:C/I:C/A:C

Severity: Medium

CVSS v3

Base Score: 8.3

Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Severity: High

EPSS

EPSS: 0.01689

Vulnerability Watch

Tenable Research has classified this CVE under the following Vulnerability Watch classification, which includes active and historical (inactive) classifications. You can learn more about these classifications on our blog.

Vulnerability Being Monitored