CVE-2026-12064— proto-default skips SSH verification
Quick assessment
Affected
curl curl
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
curl是瑞典cURL团队开源的一款用于从服务器传输数据或向服务器传输数据的工具。 curl存在加密问题漏洞，该漏洞源于工具层在使用无方案URL并配合--proto-default sftp（或scp）时错误推断URL方案，绕过了关键SSH安全选项（如CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256和CURLOPT_SSH_KNOWNHOSTS）的初始化，导致连接至未验证的SSH远程主机而不报错。
Possible ATT&CK Techniques 1 AI
T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-12064
Vulnerability Information
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Vulnerability Title
proto-default skips SSH verification
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
curl 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
curl是瑞典cURL团队开源的一款用于从服务器传输数据或向服务器传输数据的工具。 curl存在加密问题漏洞，该漏洞源于工具层在使用无方案URL并配合--proto-default sftp（或scp）时错误推断URL方案，绕过了关键SSH安全选项（如CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256和CURLOPT_SSH_KNOWNHOSTS）的初始化，导致连接至未验证的SSH远程主机而不报错。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-12064
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Advisories for CVE-2026-12064 (2)
Proof of Concept for CVE-2026-12064 (1)
Same Patch Batch · curl · 2026-07-03 · 18 CVEs total
| CVE-2026-9546 | sending old referer | |
| CVE-2026-8932 | incomplete mTLS config matching in conn reuse | |
| CVE-2026-8458 | wrong reuse for different services | |
| CVE-2026-8925 | SASL double-free | |
| CVE-2026-8286 | wrong STARTTLS connection reuse | |
| CVE-2026-8927 | env-set cross-proxy Digest auth state leak | |
| CVE-2026-8926 | password leak with netrc and user in URL | |
| CVE-2026-8924 | trailing dot domain super cookie | |
| CVE-2026-10536 | HTTP/2 stream-dependency tree UAF | |
| CVE-2026-11352 | QUIC zero-length UDP datagrams busy-loop | |
| CVE-2026-9545 | exposing HTTP/3 early data | |
| CVE-2026-9080 | UAF after pause in socket callback | |
| CVE-2026-9547 | SSH improper host validation | |
| CVE-2026-9079 | stale proxy password leak | |
| CVE-2026-11564 | Native CA trust persist | |
| CVE-2026-11856 | cross-origin Digest auth state leak | |
| CVE-2026-11586 | WS Auto-PONG memory exhaustion |
IV. Related Vulnerabilities
V. Comments for CVE-2026-12064
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