# CVE-2026-12064: proto-default skips SSH verification

> Attackers can bypass SSH host verification when curl uses schemeless URLs with specific protocol defaults, allowing connections to unverified hosts.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Jul 2026
- **Updated:** 15 Sep 2026
- **Also known as:** ALPINE-CVE-2026-12064, AZL-91812, BELL-CVE-2026-12064, CURL-CVE-2026-12064, DEBIAN-CVE-2026-12064, ECHO-2ea7-d2c8-d549, GHSA-jm94-9f7h-36pr, JLSEC-2026-1202, MINI-57vg-25pp-5hq8, MINI-7qgx-477r-f5v8, ROOT-OS-ALPINE-315-CVE-2026-12064, ROOT-OS-ALPINE-320-CVE-2026-12064, ROOT-OS-ALPINE-321-CVE-2026-12064, ROOT-OS-ALPINE-322-CVE-2026-12064, ROOT-OS-DEBIAN-11-CVE-2026-12064, ROOT-OS-DEBIAN-12-CVE-2026-12064, ROOT-OS-DEBIAN-13-CVE-2026-12064, UBUNTU-CVE-2026-12064

## What is CVE-2026-12064?

CVE-2026-12064 is a high-severity vulnerability in Haxx Curl, published on 3 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### 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.

Weakness: CWE-295 (Improper Certificate Validation), CWE-297 (Improper Validation of Certificate with Host Mismatch)

## Which versions are affected by CVE-2026-12064?

It affects 1 product.


Products: Haxx Curl.

## How do I fix CVE-2026-12064?

Apply the vendor's patch.

## Is CVE-2026-12064 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-12064 exists.

## Other vulnerabilities in Haxx Curl

- [CVE-2026-19931](https://insights.sbomify.com/CVE-2026-19931/): Negotiate ambient user conn reuse (critical 9.8)
- [CVE-2026-10536](https://insights.sbomify.com/CVE-2026-10536/): HTTP/2 stream-dependency tree UAF (critical 9.8)
- [CVE-2026-11856](https://insights.sbomify.com/CVE-2026-11856/): cross-origin Digest auth state leak (critical 9.8)
- [CVE-2026-8925](https://insights.sbomify.com/CVE-2026-8925/): SASL double-free (critical 9.8)
- [CVE-2026-9079](https://insights.sbomify.com/CVE-2026-9079/): stale proxy password leak (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-12064 and fix it if it is affected.

What it is: CVE-2026-12064 is a high-severity vulnerability in Haxx Curl, published on 3 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-12064 exists.

Affected product: Haxx Curl. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-12064/ (Markdown: https://insights.sbomify.com/CVE-2026-12064/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-12064
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12064
- OSV: https://osv.dev/vulnerability/CVE-2026-12064

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-12064/
Summaries are generated and may contain mistakes; the official description above is the record.