CVE-2025-41256 in Cyberduck
Summary
by MITRE • 06/25/2025
Cyberduck and Mountain Duck improper handle TLS certificate pinning for untrusted certificates (e.g., self-signed), since the certificate fingerprint is stored as SHA-1, although SHA-1 is considered weak.
This issue affects Cyberduck: through 9.1.6; Mountain Duck: through 4.17.5.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 06/25/2025
The vulnerability CVE-2025-41256 represents a critical security flaw in Cyberduck and Mountain Duck applications that undermines the integrity of secure communications through improper handling of TLS certificate pinning mechanisms. These applications, which are widely used for file transfer and remote desktop connections, implement certificate pinning functionality to verify the authenticity of server certificates. However, the implementation suffers from a fundamental cryptographic weakness that significantly compromises the security posture of users relying on these tools for sensitive operations. The vulnerability specifically manifests when the applications encounter untrusted certificates such as self-signed certificates, which are commonly used in development environments or internal networks where organizations need to establish secure connections without relying on publicly trusted certificate authorities.
The technical flaw stems from the use of SHA-1 hashing algorithm for storing certificate fingerprints within the application's certificate pinning mechanism. This represents a severe cryptographic weakness that has been widely recognized and deprecated by security standards organizations and major technology vendors. SHA-1 is vulnerable to collision attacks and has been deemed cryptographically broken and unsuitable for security-sensitive applications since 2005. The National Institute of Standards and Technology has explicitly recommended against using SHA-1 for any security-critical purposes, and the Internet Engineering Task Force has also deprecated its use in TLS contexts. This vulnerability directly maps to CWE-327, which addresses the use of weak cryptographic algorithms, and CWE-328, which covers the use of weak hash algorithms. The implementation of SHA-1 for certificate pinning creates a significant attack surface where malicious actors could potentially generate certificate collisions, allowing them to bypass the intended security controls and establish fraudulent connections with compromised applications.
The operational impact of this vulnerability extends beyond simple certificate validation failures and creates substantial risks for organizations using these applications in enterprise environments. When users connect to servers using self-signed certificates or other untrusted certificates, the applications' reliance on SHA-1 for fingerprint storage means that the security guarantees provided by certificate pinning are fundamentally compromised. This weakness enables man-in-the-middle attacks where attackers could potentially create colliding certificates that would be accepted by the applications, effectively nullifying the protection that certificate pinning is designed to provide. The vulnerability affects both Cyberduck versions through 9.1.6 and Mountain Duck versions through 4.17.5, indicating a widespread exposure across multiple user bases. Organizations using these applications for secure file transfers, remote desktop connections, or other sensitive operations face significant risks, particularly in environments where network security is paramount and where attackers might attempt to exploit this weakness to intercept communications or gain unauthorized access to systems.
The mitigation strategies for this vulnerability require immediate attention from system administrators and security teams responsible for maintaining these applications. The most critical remediation involves updating to the latest versions of both Cyberduck and Mountain Duck where the SHA-1 dependency has been eliminated and replaced with stronger cryptographic algorithms such as SHA-256 or SHA-3. Organizations should also consider implementing additional monitoring and detection mechanisms to identify any potential exploitation attempts targeting this vulnerability. Security teams should review their certificate management policies and ensure that certificate pinning configurations are properly implemented using modern cryptographic standards. The vulnerability also highlights the importance of adhering to security best practices as outlined in the NIST Cybersecurity Framework and ISO 27001 standards, particularly regarding the use of strong cryptographic algorithms and regular security updates. Organizations should also consider implementing network-based detection measures such as intrusion detection systems that can monitor for suspicious certificate validation patterns or anomalous connection behaviors that might indicate exploitation attempts. Given the nature of the vulnerability and its potential for exploitation in enterprise environments, immediate patching and verification of certificate pinning configurations should be prioritized as part of comprehensive security maintenance procedures.