CVE-2023-40547
HighCVSS 8.3Exploitation Probability (EPSS)
Very high risk91th percentile - higher than 91% of all known CVEs
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.
Risk Assessment
The risk is the possibility of complete system compromise by an attacker who can perform a Man-in-the-Middle attack or compromise the boot server. However, the vulnerability is only exploitable during the early boot phase.
Recommendation
It is recommended to immediately update Shim to the latest patched version and secure boot servers against unauthorized access.
Original NVD description (English source)
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.