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.

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploitation poc

Automatable no

Technical Impact total

Affected Vendors & Products

Vendors Products
Curl
  • Curl

No data.

No data.

References
Link Providers
https://curl.se/docs/CVE-2026-9547.html cve-icon cve-icon
https://curl.se/docs/CVE-2026-9547.json cve-icon cve-icon
https://hackerone.com/reports/3751712 cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-9547 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-9547 cve-icon
History

Tue, 07 Jul 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-347
References
Metrics threat_severity

None

 threat_severity

Important

Mon, 06 Jul 2026 22:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-295
CWE-307

Mon, 06 Jul 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Mon, 06 Jul 2026 04:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-295
CWE-307

Sun, 05 Jul 2026 20:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-295

Sun, 05 Jul 2026 09:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-295

Sun, 05 Jul 2026 01:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-295

Sat, 04 Jul 2026 09:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-295

Fri, 03 Jul 2026 21:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-287

Fri, 03 Jul 2026 10:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-287

Fri, 03 Jul 2026 08:30:00 +0000

Type Values Removed Values Added
First Time appeared Curl
Curl curl
Vendors & Products Curl
Curl curl

Fri, 03 Jul 2026 06:45:00 +0000

Type Values Removed Values Added
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.
Title SSH improper host validation
References
cve-icon MITRE

Status: PUBLISHED

Assigner: curl

Published: 2026-07-03T06:18:44.499Z

Updated: 2026-07-06T16:48:14.469Z

Reserved: 2026-05-26T06:45:27.665Z

Link: CVE-2026-9547

cve-icon Vulnrichment

Updated: 2026-07-06T16:48:09.620Z

cve-icon NVD

No data.

cve-icon Redhat

Severity : Important

Publid Date: 2026-07-03T06:18:44Z

Links: CVE-2026-9547 - Bugzilla