CVE-2023-40547

Publication date 23 January 2024

Last updated 24 July 2024

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

9.0 · Critical

Score breakdown

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.

Read the notes from the security team

Status

Package Ubuntu Release Status
secureboot-db 24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Not affected
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty
Not affected
shim 24.10 oracular
Fixed 15.8-0ubuntu1
24.04 LTS noble
Fixed 15.8-0ubuntu1
23.10 mantic Ignored end of life, was needed
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
Vulnerable
20.04 LTS focal
Vulnerable
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial Ignored install media keys will never be revoked
14.04 LTS trusty Ignored end of ESM support, was ignored [install media keys will never be revoked]
shim-signed 24.10 oracular
Fixed 1.58
24.04 LTS noble
Fixed 1.58
23.10 mantic Ignored end of life, was needed
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
Vulnerable
20.04 LTS focal
Vulnerable
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial Ignored install media keys will never be revoked
14.04 LTS trusty Ignored end of ESM support, was ignored [install media keys will never be revoked]

Notes

eslerm

UEFI Security Response Team states that dbx update is not needed secureboot-db should only ever be updated after shim secureboot-db is not updated on ESM releases as doing so would revoke install media keys Note that key revocation is required to protect against evil housekeeper attacks (such as BlackLotus)

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
shim

Severity score breakdown

Parameter Value
Base score 9.0 · Critical
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Scope Changed
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H