CVE-2026-40242 Arcane Unauthenticated SSRF with Conditional Response Reflection in Template Fetch Endpoint
Unauthenticated attackers can exploit an SSRF vulnerability in the template fetch endpoint to read internal server responses.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40242?
CVE-2026-40242 is a high-severity server-side request forgery vulnerability in getarcaneapp arcane, published on 10 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Arcane is an interface for managing Docker containers, images, networks, and volumes. Prior to 1.17.3, the /api/templates/fetch endpoint accepts a caller-supplied url parameter and performs a server-side HTTP GET request to that URL without authentication and without URL scheme or host validation. The server's response is returned directly to the caller. type. This constitutes an unauthenticated SSRF vulnerability affecting any publicly reachable Arcane instance. This vulnerability is fixed in 1.17.3.
Weakness: CWE-918
Which versions are affected by CVE-2026-40242?
3 open source packages ship an affected version, including github.com/getarcaneapp/arcane/backend. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/getarcaneapp/arcane/backend Go | All versions | 1.17.3 |
github.com/getarcaneapp/arcane/backend Go | All versions | 1.17.3 |
github.com/getarcaneapp/arcane/backend Go | All versions | 1.17.3 |
Products include Getarcane Arcane.
How do I fix CVE-2026-40242?
Upgrade github.com/getarcaneapp/arcane/backend to 1.17.3 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-40242 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40242 exists.
Public exploit code: 1 Nuclei template.
Other vulnerabilities in getarcaneapp arcane
Sources
Also known as GHSA-ff24-4prj-gpmj, GO-2026-5356.