CVE-2025-41255 in Cyberduck
Summary
by MITRE • 06/25/2025
Cyberduck and Mountain Duck improperly handle TLS certificate pinning for untrusted certificates (e.g., self-signed), unnecessarily installing it to the Windows Certificate Store of the current user without any restrictions.
This issue affects Cyberduck through 9.1.6 and Mountain Duck through 4.17.5.
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Analysis
by VulDB Data Team • 06/25/2025
The vulnerability identified as CVE-2025-41255 represents a critical certificate handling flaw in Cyberduck and Mountain Duck applications that directly impacts the security of TLS connections on Windows systems. This issue stems from improper implementation of certificate pinning mechanisms, where the applications fail to properly validate certificate trust chains when encountering untrusted certificates such as self-signed certificates. The flaw allows these applications to automatically install untrusted certificates into the Windows Certificate Store of the current user without implementing any access controls or validation checks, creating a significant security risk for end users.
The technical implementation of this vulnerability demonstrates a failure in proper certificate validation procedures and privilege management within the Windows operating environment. When Cyberduck or Mountain Duck encounters an untrusted certificate during TLS connection establishment, instead of rejecting the certificate or properly warning the user about the security implications, the applications proceed to install the certificate into the user's certificate store. This behavior violates fundamental security principles of certificate trust management and creates a persistent threat vector that can be exploited by malicious actors who have access to the local system. The vulnerability specifically affects versions through Cyberduck 9.1.6 and Mountain Duck 4.17.5, indicating this flaw has persisted across multiple releases without proper remediation.
The operational impact of this vulnerability extends beyond simple certificate management issues and creates a substantial attack surface for privilege escalation and man-in-the-middle attacks. By installing untrusted certificates into the Windows Certificate Store, the applications essentially provide malicious actors with a persistent foothold that can be leveraged to intercept encrypted communications or impersonate legitimate services. This behavior is particularly concerning because it operates silently in the background without user awareness, potentially allowing attackers to establish persistent monitoring capabilities. The installation of certificates into the user store means that any application or process running under that user context can now trust these previously untrusted certificates, effectively bypassing the normal certificate validation mechanisms that protect against certificate fraud.
Security implications of this vulnerability align with common attack patterns described in the MITRE ATT&CK framework, particularly in the privilege escalation and credential access domains. The behavior maps to techniques involving certificate manipulation and trust store modification, which are commonly used by adversaries to establish persistent access to systems. From a CWE perspective, this vulnerability manifests as a weakness in certificate validation and improper privilege management, specifically CWE-295 for certificate validation issues and CWE-732 for incorrect permissions for critical resources. The flaw represents a failure in proper input validation and trust management, creating opportunities for attackers to manipulate the certificate trust model of the operating system.
Mitigation strategies for this vulnerability should focus on immediate application updates to versions that properly implement certificate validation and trust management. System administrators should conduct thorough audits of certificate stores to identify and remove any suspicious certificates that may have been installed through this vulnerability. Network monitoring should be enhanced to detect unusual certificate installation patterns or certificate trust changes that might indicate exploitation attempts. Additionally, organizations should implement strict certificate policy enforcement and regularly review certificate trust configurations to prevent unauthorized certificate installations. The recommended approach includes disabling automatic certificate installation features, implementing certificate trust restrictions, and establishing proper user access controls to prevent unauthorized modifications to the certificate store.