Executive brief
curl is a widely used tool and library for transferring data over various network protocols. A security flaw was identified in how it handles secure file transfers (SFTP) when using a specific technical component called wolfSSH. This flaw prevents the software from verifying the identity of the remote server, which could allow an attacker to intercept or manipulate data during transmission without being detected.
Technical details
A vulnerability exists in curl's wolfSSH backend where host verification mechanisms were omitted during the implementation of SFTP support. This flaw (CWE-322) means curl does not verify the remote host's identity against a known_hosts file, making it susceptible to man-in-the-middle (MITM) attacks. The issue specifically affects builds of curl configured to use wolfSSH as the SSH backend; other backends like libssh2 or libssh are not impacted. The vulnerability was addressed in curl 8.17.0 by completely removing support for the wolfSSH backend, which was considered incomplete and experimental.
Affected products
- haxx curl 7.69.0 to 8.16.0
Timeline
- 2025-09-23: disclosed: Reported to the curl project by Stanislav Fort.
- 2025-11-05: patched: Fixed in curl version 8.17.0.
- 2025-11-07: advisory: NVD publication date.