CVE-2023-36377 is a buffer overflow vulnerability identified in the mtrojnar osslsigncode utility, version 2.3 and earlier. Osslsigncode is an open-source tool used primarily for digitally signing Windows executables (.exe), system drivers (.sys), and dynamic link libraries (.dll). The vulnerability arises when the tool processes specially crafted files, leading to a buffer overflow condition. This overflow can be exploited by a local attacker who has the ability to supply maliciously crafted files to the osslsigncode process. Successful exploitation allows the attacker to execute arbitrary code with the privileges of the osslsigncode process, potentially leading to privilege escalation or system compromise. The flaw affects the integrity and confidentiality of the affected systems by enabling unauthorized code execution. No public exploits or proof-of-concept code have been reported, and no official patch or CVSS score is currently available. The vulnerability was reserved on June 21, 2023, and published on July 3, 2023. Since osslsigncode is used in software development and deployment pipelines, especially for signing Windows binaries, this vulnerability could impact organizations that rely on it for secure code signing and verification. The attack requires local access, which limits remote exploitation but does not eliminate risk in environments where multiple users have access or where attackers have gained initial footholds.

For European organizations, the impact of CVE-2023-36377 could be significant in environments where osslsigncode is used to sign or verify Windows executables and drivers. Exploitation could allow attackers to execute arbitrary code locally, potentially leading to privilege escalation, unauthorized code execution, or tampering with signed binaries. This could undermine software supply chain integrity and trust in signed code, affecting sectors such as software development, manufacturing, and critical infrastructure. Organizations with multi-user systems or development environments are at higher risk. The vulnerability could also facilitate lateral movement within networks if attackers gain local access. Although no known exploits exist in the wild, the potential for damage warrants proactive mitigation. The impact on confidentiality, integrity, and availability is high if exploited, especially in sensitive or regulated environments common in Europe.

1. Monitor for and apply patches or updates from the osslsigncode maintainers as soon as they become available. 2. Restrict local access to systems running osslsigncode to trusted users only, minimizing the risk of local exploitation. 3. Implement strict file validation and scanning of executables, drivers, and DLLs before processing with osslsigncode to detect malformed or suspicious files. 4. Employ application whitelisting and endpoint protection to detect and block unauthorized code execution attempts. 5. Use sandboxing or isolated environments for code signing operations to contain potential exploitation. 6. Audit and monitor osslsigncode usage logs for unusual activity that could indicate exploitation attempts. 7. Educate developers and system administrators about the vulnerability and the importance of secure handling of signing tools and files. 8. Consider alternative code signing tools with active maintenance and security support if osslsigncode updates are delayed.