CVE-2026-9547
Published: June 26, 2026Last modified: July 6, 2026
Description
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.
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score | 7.4 |
| Attack Vector | NETWORK |
| Attack complexity | HIGH |
| Privileges required | NONE |
| User interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality | HIGH |
| Integrity impact | HIGH |
| Availability impact | NONE |
| Vector | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N |
Status
| Product | Release | Package | Status |
|---|---|---|---|
| Alpaquita Linux | 23 LTS | curl | Fixed (8.21.0-r0) |
| 25 LTS | curl | Fixed (8.21.0-r0) | |
| Stream | curl | Fixed (8.21.0-r0) | |
| Hardened Containers | Stream | curl | Fixed (8.21.0-r0) |