Vulnerability · Published Jul 3, 2026 · Assigned by curl
CVE-2026-12064proto-default skips SSH verification
High 7.5
In plain English
A high-severity security flaw in curl from curl. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 36% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | curl | 8.22.0-r0 | ALPINE-CVE-2026-12064 |
| Alpine:v3.24 | curl | 8.21.0-r0 | ALPINE-CVE-2026-12064 |
| Debian:12 | curl | no fix listed | DEBIAN-CVE-2026-12064 |
| Debian:13 | curl | no fix listed | DEBIAN-CVE-2026-12064 |
| Debian:14 | curl | 8.21.0~rc3-1 | DEBIAN-CVE-2026-12064 |
| Ubuntu:25.10 | curl | 8.14.1-2ubuntu1.5 | UBUNTU-CVE-2026-12064 |
| Ubuntu:26.04:LTS | curl | 8.18.0-1ubuntu2.3 | UBUNTU-CVE-2026-12064 |
Affected products (as reported)
Weakness: CWE-297 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N