When a user invokes curl using a schemeless URL combined with `--proto-default` sftp (or scp), a disconnect occurs between the tool layer and libcurl. The tool layer incorrectly infers the URL scheme, which erroneously bypasses the initialization of critical SSH security options like CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256 and CURLOPT_SSH_KNOWNHOSTS. Conversely, the libcurl runtime successfully honors CURLOPT_DEFAULT_PROTOCOL and establishes the connection via SFTP/SCP as specified. Because the tool layer skipped the security configuration, these SSH host verification options are silently omitted, causing curl to connect to an unverified SSH remote host without throwing an error.

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

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 yes

Technical Impact partial

Affected Vendors & Products

Vendors Products
Curl
  • Curl

No data.

No data.

References
Link Providers
https://curl.se/docs/CVE-2026-12064.html cve-icon cve-icon
https://curl.se/docs/CVE-2026-12064.json cve-icon cve-icon
https://hackerone.com/reports/3797526 cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-12064 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-12064 cve-icon
History

Tue, 07 Jul 2026 20:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-760

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

Type Values Removed Values Added
Weaknesses CWE-358
References
Metrics threat_severity

None

 threat_severity

Important

Mon, 06 Jul 2026 19:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-760
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Mon, 06 Jul 2026 13:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-287

Mon, 06 Jul 2026 01:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-287

Sun, 05 Jul 2026 20:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-287

Sat, 04 Jul 2026 20:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-287

Sat, 04 Jul 2026 09:45:00 +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 07:45:00 +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 user invokes curl using a schemeless URL combined with `--proto-default` sftp (or scp), a disconnect occurs between the tool layer and libcurl. The tool layer incorrectly infers the URL scheme, which erroneously bypasses the initialization of critical SSH security options like CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256 and CURLOPT_SSH_KNOWNHOSTS. Conversely, the libcurl runtime successfully honors CURLOPT_DEFAULT_PROTOCOL and establishes the connection via SFTP/SCP as specified. Because the tool layer skipped the security configuration, these SSH host verification options are silently omitted, causing curl to connect to an unverified SSH remote host without throwing an error.
Title proto-default skips SSH verification
References
cve-icon MITRE

Status: PUBLISHED

Assigner: curl

Published: 2026-07-03T06:13:55.302Z

Updated: 2026-07-06T18:21:00.665Z

Reserved: 2026-06-12T07:23:29.455Z

Link: CVE-2026-12064

cve-icon Vulnrichment

Updated: 2026-07-06T18:20:42.959Z

cve-icon NVD

No data.

cve-icon Redhat

Severity : Important

Publid Date: 2026-07-03T06:13:55Z

Links: CVE-2026-12064 - Bugzilla