high CVSS 7.5

CVE-2026-42461·Docker vulnerability

Arcane is an interface for managing Docker containers, images, networks, and volumes. Prior to version 1.18.0, four GET endpoints under /api/templates* in Arcane's Huma backend are registered without any Security requirement, allowing any unauthenticated network client to list and read the full Compose YAML and .env content of every custom template stored in the instance. Because Arcane's UI exposes a "Save as Template" flow on the project / swarm-stack creation pages that persists the operator's real env content (database passwords, API keys, etc.) verbatim, this missing authorization is an unauthenticated read of operator secrets in practice — not a theoretical info-disclosure. The frontend explicitly treats /customize/templates/* as an authenticated area (PROTECTED_PREFIXES in frontend/src/lib/utils/redirect.util.ts), and every CRUD operation (POST/PUT/DELETE) on the same paths requires a Bearer/API key, so this is a clear backend authorization gap, not intended public access. This issue has been patched in version 1.18.0.

Severity: high
Software: Docker
Fixed in: 1.18.0
Published: 2026-05-09

Affected versions

Until: 1.18.0

Fixed in: 1.18.0

How to fix this CVE

Upgrade Docker to version 1.18.0 or later to patch the Arcane template API authorization bypass. This vulnerability allows unauthenticated attackers to read sensitive environment variables and secrets stored in Docker Compose templates. Immediately apply the update to prevent unauthorized disclosure of database passwords, API keys, and other credentials.

sudo dnf update docker-ce

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

GET /api/templates/.* HTTP/1.1.*200|GET /api/templates/list HTTP.*200|GET /customize/templates/.* HTTP.*200.*yaml|GET /customize/templates/.* HTTP.*200.*env

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch.

Implement authentication middleware on all /api/templates* endpoints requiring valid Bearer token or API key in Authorization header; block GET requests to /api/templates* returning HTTP 200 without valid auth credentials; enforce rate limiting on /api/templates/* endpoints to 10 requests per minute per IP.

How to check if you are affected

Check Docker version: docker --version or docker version
Verify Arcane backend service is running: docker ps | grep arcane or systemctl status docker
Search API access logs for unauthenticated GET requests to /api/templates* endpoints: grep -r 'GET /api/templates' /var/log/docker* or equivalent container logs
Confirm the fix by checking if /api/templates* endpoints now return 401 Unauthorized for requests without Bearer token authentication

Indicators of compromise

/api/templates/list
/api/templates/read
/customize/templates/
GET /api/templates* 200 response containing yaml or env content

FAQ

What is CVE-2026-42461?

CVE-2026-42461 is an authentication bypass vulnerability in Arcane's template management API that allows unauthenticated attackers to retrieve and read Compose YAML files and environment variables containing sensitive credentials like database passwords and API keys.

Is CVE-2026-42461 being actively exploited?

No, CVE-2026-42461 is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits are currently available, though the vulnerability is trivial to exploit.

What versions of Docker are affected by CVE-2026-42461?

All versions of Arcane prior to version 1.18.0 are affected. The vulnerability exists in Docker installations running Arcane as a management interface.

How do I check if my server is vulnerable to CVE-2026-42461?

Run: docker version or docker --version to check your Docker version. If running Arcane below 1.18.0, attempt a curl request: curl http://localhost:8000/api/templates/list without authentication headers; if it returns template data, your system is vulnerable.

Does Defensia detect CVE-2026-42461?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Docker is installed on a monitored server, CVE-2026-42461 will appear in your dashboard with remediation steps.

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References

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