Overview
The vulnerability CVE-2025-41256 highlights an improper handling of TLS certificate pinning in Cyberduck and Mountain Duck. The affected software fails to properly pin untrusted certificates, particularly self-signed ones, due to the usage of the SHA-1 hashing algorithm, which is known to be weak. This vulnerability could potentially lead to system compromise or data leakage, posing a significant risk to users and organizations who rely on these software for their operations.
Vulnerability Summary
CVE ID: CVE-2025-41256
Severity: High (7.4/10)
Attack Vector: Network
Privileges Required: None
User Interaction: Required
Impact: Potential system compromise or data leakage
Affected Products
Product | Affected Versions
Cyberduck | up to 9.1.6
Mountain Duck | up to 4.17.5
How the Exploit Works
The exploiter can take advantage of this vulnerability by posing as a legitimate entity and presenting a self-signed certificate. Since the software improperly pins this untrusted certificate and stores the certificate fingerprint as weak SHA-1, it becomes susceptible to a ‘man-in-the-middle’ (MitM) attack. By intercepting and altering communications between two parties, an attacker could potentially compromise the system or leak sensitive data.
Conceptual Example Code
Below is a conceptual example of how this vulnerability might be exploited. In this case, the attacker presents a self-signed certificate during the TLS handshake.
POST /tls-handshake HTTP/1.1
Host: target.example.com
Content-Type: application/tls-certificate
{ "certificate": "self-signed-certificate", "fingerprint": "SHA-1-fingerprint" }
Upon receiving this request, the vulnerable software would improperly pin the untrusted self-signed certificate, opening up the possibility for a ‘man-in-the-middle’ attack.
