CVE-2026-12064

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://curl.se/docs/CVE-2026-12064.html	Patch Vendor Advisory
https://curl.se/docs/CVE-2026-12064.json	Vendor Advisory
https://hackerone.com/reports/3797526	Exploit Issue Tracking Third Party Advisory
https://hackerone.com/reports/3797526	Exploit Issue Tracking Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-07-03 07:16

Updated : 2026-09-15 07:16

NVD link : CVE-2026-12064

Mitre link : CVE-2026-12064

CVE.ORG link : CVE-2026-12064

JSON object : View

Products Affected

haxx

curl

CWE

CWE-297

Improper Validation of Certificate with Host Mismatch

CWE-295

Improper Certificate Validation

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The tool layer incorrectly infers the URL scheme, which\nerroneously bypasses the initialization of critical SSH security options like\nCURLOPT_SSH_HOST_PUBLIC_KEY_SHA256 and CURLOPT_SSH_KNOWNHOSTS. Conversely, the\nlibcurl runtime successfully honors CURLOPT_DEFAULT_PROTOCOL and establishes\nthe connection via SFTP/SCP as specified. Because the tool layer skipped the\nsecurity configuration, these SSH host verification options are silently\nomitted, causing curl to connect to an unverified SSH remote host without\nthrowing an error."}], "lastModified": "2026-09-15T07:16:26.150", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "53E9B785-AB1F-48AC-B737-EEB59C80E5BF", "versionEndExcluding": "8.21.0", "versionStartIncluding": "7.81.0"}], "operator": "OR"}]}], "sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9"}