CVE-2026-12064 — curl
HIGHCVE-2026-12064 is a high-severity (CVSS 7.5) CWE-297 vulnerability. A fix is available — see the affected versions and patch details below.
proto-default skips SSH verification
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-12064.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-12064 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 380,526 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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 Products
curlhaxxDetection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Fix
Upgrade the affected component to the fixed release for CVE-2026-12064, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This Important flaw in curl allows an attacker to bypass SSH host verification when a user invokes curl with a schemeless URL and specifies SFTP or SCP as the default protocol. This can lead to man-in-the-middle attacks, enabling data interception or manipulation without user awareness in Red Hat environments.
To mitigate this issue, avoid using the `--proto-default sftp` or `--proto-default scp` options with schemeless URLs when invoking the `curl` command. Instead, explicitly specify the protocol in the URL (e.g., `sftp://host/path` or `scp://host/path`).Source: Red Hat security advisory for CVE-2026-12064 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 10 | curl-0:8.12.1-4.el10_2.3 | RHSA-2026:55450 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | curl-0:8.12.1-1.el10_0.10 | RHSA-2026:72506 |
| Red Hat Hardened Images | curl-main-8.21.0-0.1.hum1 | RHSA-2026:29017 |
| Red Hat Hardened Images | rust-main-1.96.1-1.hum1 | RHSA-2026:34975 |
Frequently Asked Questions
Is CVE-2026-12064 in your dependencies?
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