CVE-2025-51726 identifies critical security weaknesses in the CyberGhostVPNSetup.exe Windows installer. The installer is signed using the deprecated SHA-1 cryptographic hash algorithm, which is vulnerable to collision attacks. This vulnerability enables an attacker to create a malicious installer with a forged SHA-1 signature that could be accepted by Windows signature verification mechanisms, especially on systems lacking strict SmartScreen or trust policy enforcement. This undermines the trust model of code signing, allowing supply-chain style attacks where users may unknowingly install compromised software. Additionally, the installer binary does not implement High Entropy Address Space Layout Randomization (ASLR), as confirmed by BinSkim (BA2015 rule) and WinDbg analysis. Without high entropy ASLR, the binary loads into predictable memory addresses, significantly increasing the likelihood of successful memory corruption exploits such as buffer overflows or use-after-free vulnerabilities. The combination of weak signature verification and predictable memory layout substantially lowers the difficulty for attackers to perform privilege escalation or execute arbitrary code via fake installers. Although no known exploits are currently reported in the wild, these weaknesses present a serious risk to the integrity and security of systems running this installer, particularly in environments with lax signature verification policies or outdated Windows versions. The absence of a CVSS score necessitates an assessment based on the potential impact and exploitability factors.

For European organizations, this vulnerability poses a significant threat to endpoint security and supply chain integrity. CyberGhost VPN is a popular VPN service in Europe, often used by enterprises and individuals to secure communications and bypass censorship. A compromised installer could lead to widespread deployment of malicious software masquerading as legitimate VPN clients, resulting in unauthorized access, data exfiltration, or lateral movement within corporate networks. The predictable memory layout increases the risk of privilege escalation on affected endpoints, potentially allowing attackers to gain administrative control. This is particularly concerning for organizations in regulated sectors such as finance, healthcare, and government, where data confidentiality and system integrity are paramount. Furthermore, the reliance on Windows signature verification mechanisms means that organizations with outdated or misconfigured security policies are more vulnerable. The threat could also undermine trust in VPN solutions, impacting remote work security postures across Europe.

Organizations should immediately verify the authenticity of any CyberGhostVPNSetup.exe installers before deployment, preferably by obtaining installers from official, trusted sources and validating their signatures with updated cryptographic standards. Users and administrators should ensure that Windows SmartScreen and trust policies are strictly enforced and updated to reject SHA-1 signed binaries. Applying application whitelisting and endpoint detection and response (EDR) solutions can help detect anomalous installer behavior. It is critical to monitor for updates from CyberGhost VPN that address these issues, specifically a re-signed installer using SHA-256 or stronger hashes and implementation of high entropy ASLR. Until patched versions are available, organizations should consider restricting installation of this VPN client or deploying it in controlled environments. Security teams should also conduct memory protection hardening and regularly audit endpoint configurations to mitigate exploitation risks. Finally, educating users about the risks of installing software from unverified sources will reduce the likelihood of successful social engineering attacks leveraging this vulnerability.