#VU86236 Insufficient verification of data authenticity in Shim - CVE-2023-40547

Vulnerability identifier: #VU86236

Vulnerability risk: High

CVSSv4.0: 7.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]

CVE-ID: CVE-2023-40547

CWE-ID: CWE-345

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Shim
Universal components / Libraries / Libraries used by multiple products

Vendor: Red Hat Bootloader Team

Description

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to missing verification of data authenticity when parsing HTTP responses. A remote attacker can perform a man-in-the-middle (MitM) attack and use 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.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Shim: 0.3 - 15.7

---

External links
https://access.redhat.com/security/cve/CVE-2023-40547
https://bugzilla.redhat.com/show_bug.cgi?id=2234589
https://www.openwall.com/lists/oss-security/2024/01/26/1

---

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.