CVE-2023-40549 is a medium-severity vulnerability identified in the Shim component of Red Hat Enterprise Linux 7. Shim is a small bootloader used in the UEFI Secure Boot process to load signed bootloaders and kernels. The vulnerability arises from an out-of-bounds read flaw caused by insufficient boundary verification when loading Portable Executable (PE) binaries. An attacker can craft a malicious PE binary that triggers this flaw, causing Shim to read beyond the allocated memory bounds. This leads to a crash of the Shim process, resulting in a denial of service (DoS) condition during system boot. The vulnerability does not impact confidentiality or integrity, as it does not allow code execution or data leakage, but it affects system availability by preventing successful booting. Exploitation requires local access with the ability to supply a crafted PE binary to the boot process, and no user interaction or privileges are needed beyond local access. The CVSS v3.1 score is 6.2, reflecting medium severity with an attack vector of local (AV:L), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), and impact limited to availability (A:H). No known exploits are currently reported in the wild, and no patches or mitigation links are provided in the source data, indicating that organizations should monitor Red Hat advisories for updates.

For European organizations relying on Red Hat Enterprise Linux 7, this vulnerability poses a risk primarily to system availability. Systems using Shim for Secure Boot could fail to boot if exposed to a crafted PE binary, potentially causing downtime in critical infrastructure, servers, or embedded devices. This is particularly impactful for environments where physical or local access is possible by untrusted personnel or where automated processes load PE binaries during boot. While the vulnerability does not allow data compromise or privilege escalation, denial of service during boot can disrupt business continuity, especially in sectors like finance, healthcare, manufacturing, and government services that depend on high availability and secure boot chains. The lack of remote exploitability reduces the risk of widespread attacks but does not eliminate the threat in environments with shared physical access or compromised internal networks.

Organizations should implement the following specific mitigations: 1) Restrict physical and local access to systems running Red Hat Enterprise Linux 7 to trusted personnel only, minimizing the risk of an attacker supplying crafted PE binaries. 2) Monitor Red Hat security advisories closely and apply patches or updates for Shim as soon as they become available to address this vulnerability. 3) Implement boot process integrity checks and logging to detect abnormal boot failures potentially caused by malformed PE binaries. 4) Use hardware-based security features such as TPM and secure boot policies to restrict the loading of unauthorized binaries. 5) For critical systems, consider upgrading to newer Red Hat Enterprise Linux versions where this vulnerability is not present or has been addressed. 6) Conduct regular audits of bootloader configurations and ensure that only signed and verified binaries are used in the boot process.