When a libcurl-based application performs transfers via `SCP://` or `SFTP://` and utilizes the `CURLOPT_SSH_KEYFUNCTION` callback, it may silently accept an untrusted server. This vulnerability occurs when a server presents a host key type that does not match the specific key type already recorded for that host in the `known_hosts` file. Instead of rejecting the mismatch, the callback mechanism fails to properly enforce the restriction, allowing the connection to succeed without warning and risk
When a libcurl-based application performs transfers via SCP:// or SFTP://
and utilizes the CURLOPT_SSH_KEYFUNCTION callback, it may silently accept an
untrusted server. This vulnerability occurs when a server presents a host key
type that does not match the specific key type already recorded for that host
in the known_hosts file. Instead of rejecting the mismatch, the callback
mechanism fails to properly enforce the restriction, allowing the connection
to succeed without warning and risking a potential man-in-the-middle attack.
Why this VPI (explainable, experimental)
VPI breakdown
| Impact | 74.00 |
| Exploitation signal(PoC exists) | ×1.20 |
| VPI | 88.80 |
VPI formula vpi-v1
This CVE is referenced in a KISA security bulletin (Korean only).