CVE-2023-47039 is a heap-based buffer overflow vulnerability found in Perl for Windows, specifically related to how Perl locates and executes the Windows shell executable cmd.exe. When Perl runs an executable that depends on the Windows Perl interpreter, it attempts to find cmd.exe by searching directories in the system PATH environment variable. However, due to a flaw in the path search order, Perl first looks in the current working directory before searching system directories. This behavior can be exploited by an attacker with limited privileges who can write files to locations with weak permissions, such as C:\ProgramData. By placing a malicious cmd.exe in such a directory, the attacker can cause Perl to execute this malicious binary instead of the legitimate system cmd.exe. This leads to arbitrary code execution with the privileges of the user running the Perl executable, which may be an administrator. The vulnerability affects Perl versions 0, 5.36.0, and 5.38.0 and was published on January 2, 2024. The CVSS 3.1 score is 7.8, reflecting high severity due to the potential for full system compromise. Exploitation requires local access with limited privileges but does not require user interaction. No known exploits are currently reported in the wild. The root cause is the insecure search order for cmd.exe, combined with writable directories in the system path, which allows privilege escalation via path hijacking. This vulnerability impacts confidentiality, integrity, and availability by enabling attackers to execute arbitrary code and potentially take full control of affected systems.

For European organizations, this vulnerability poses a significant risk, especially in environments where Perl scripts are used on Windows systems with shared or weakly protected directories such as C:\ProgramData. Attackers with limited local access can escalate privileges to administrative levels, potentially leading to full system compromise. This can result in data breaches, disruption of critical services, and unauthorized access to sensitive information. Organizations in sectors like finance, healthcare, government, and critical infrastructure that rely on Perl for automation or scripting on Windows platforms are particularly vulnerable. The ability to execute arbitrary code with elevated privileges can facilitate lateral movement within networks, persistence, and deployment of ransomware or other malware. The absence of required user interaction lowers the barrier for exploitation once local access is obtained. The vulnerability also highlights the risk of improper file system permissions and the importance of secure environment configurations in preventing privilege escalation attacks.

1. Immediately restrict write permissions on directories commonly included in the system PATH, such as C:\ProgramData, to prevent unprivileged users from placing executables there. 2. Avoid running Perl scripts from directories that are writable by non-administrative users. 3. Implement application whitelisting or executable allowlisting to prevent unauthorized binaries from executing. 4. Monitor and audit directories in the system PATH for unexpected or suspicious executables named cmd.exe or similar. 5. Use fully qualified paths or environment variables that explicitly specify the system cmd.exe location in Perl scripts or wrappers to avoid reliance on the current directory search order. 6. Apply patches or updates from Perl maintainers as soon as they become available to address this vulnerability. 7. Employ endpoint detection and response (EDR) solutions to detect anomalous process executions indicative of exploitation attempts. 8. Educate system administrators and developers about the risks of insecure directory permissions and path hijacking attacks. 9. Consider running Perl scripts with the least privilege necessary and avoid administrative privileges unless absolutely required. 10. Regularly review and harden system PATH environment variables to minimize exposure to path hijacking.