CVE-2026-12064

UNKNOWN 0.0

proto-default skips SSH verification

CVSS Score

0.0

EPSS Score

0.0%

EPSS Percentile

0th

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.

Vendor	curl
Product	curl
Published	Jul 3, 2026

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Affected Versions

curl / curl

8.20.0 ≤ 8.20.0 8.19.0 ≤ 8.19.0 8.18.0 ≤ 8.18.0 8.17.0 ≤ 8.17.0 8.16.0 ≤ 8.16.0 8.15.0 ≤ 8.15.0 8.14.1 ≤ 8.14.1 8.14.0 ≤ 8.14.0 8.13.0 ≤ 8.13.0 8.12.1 ≤ 8.12.1 8.12.0 ≤ 8.12.0 8.11.1 ≤ 8.11.1 8.11.0 ≤ 8.11.0 8.10.1 ≤ 8.10.1 8.10.0 ≤ 8.10.0 8.9.1 ≤ 8.9.1 8.9.0 ≤ 8.9.0 8.8.0 ≤ 8.8.0 8.7.1 ≤ 8.7.1 8.7.0 ≤ 8.7.0 8.6.0 ≤ 8.6.0 8.5.0 ≤ 8.5.0 8.4.0 ≤ 8.4.0 8.3.0 ≤ 8.3.0 8.2.1 ≤ 8.2.1 8.2.0 ≤ 8.2.0 8.1.2 ≤ 8.1.2 8.1.1 ≤ 8.1.1 8.1.0 ≤ 8.1.0 8.0.1 ≤ 8.0.1 8.0.0 ≤ 8.0.0 7.88.1 ≤ 7.88.1 7.88.0 ≤ 7.88.0 7.87.0 ≤ 7.87.0 7.86.0 ≤ 7.86.0 7.85.0 ≤ 7.85.0 7.84.0 ≤ 7.84.0 7.83.1 ≤ 7.83.1 7.83.0 ≤ 7.83.0 7.82.0 ≤ 7.82.0 7.81.0 ≤ 7.81.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

curl.se: https://curl.se/docs/CVE-2026-12064.json curl.se: https://curl.se/docs/CVE-2026-12064.html hackerone.com: https://hackerone.com/reports/3797526

Credits

alienowo on hackerone (AntAISecurityLab) Daniel Stenberg