# CVE-2026-40242: Arcane SSRF in template fetch endpoint

Source: https://junglewise.ai/threats/cve-2026-40242-arcane-ssrf-in-template-fetch-endpoint  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-10. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2026-40242 · Severity: high · CVSS 7.2 · Published 2026-04-10

Arcane, an application for managing templates, contains a security flaw in its template fetching feature. An unauthenticated attacker can use the server to send requests to internal network services that are not normally accessible from the internet. This could allow an attacker to scan internal networks, discover private services, or access sensitive internal dashboards and APIs.

Technologies: [Arcane backend](https://junglewise.ai/threats/technologies/arcane-backend), [Getarcane Arcane](https://junglewise.ai/threats/technologies/arcane), [github.com/getarcaneapp/arcane/backend (Go)](https://junglewise.ai/threats/technologies/github-com-getarcaneapp-arcane-backend). Vendors: [Arcane](https://junglewise.ai/threats/vendors/arcane), [Getarcane](https://junglewise.ai/threats/vendors/getarcane), [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-40242 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-40242 being exploited in the wild.

**How severe is CVE-2026-40242?** High severity, with a CVSS score of 7.2, published 10 April 2026.

**Which products and versions are affected?** Arcane backend <= 1.17.2; github.com/getarcaneapp/arcane/backend (Go) <= 1.17.2, SEMVER:introduced=0,fixed=1.17.3.

**Is there a fix for CVE-2026-40242?** Yes. github.com/getarcaneapp/arcane/backend (Go): upgrade to 1.17.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-40242 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-40242?** Check whether you run Arcane backend, Getarcane Arcane or github.com/getarcaneapp/arcane/backend (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/getarcaneapp/arcane/backend (Go): upgrade to 1.17.3 or later

  ```sh
  go get github.com/getarcaneapp/arcane/backend@v1.17.3
  ```


## Technical details

An unauthenticated SSRF vulnerability exists in the /api/templates/fetch endpoint of Arcane due to a lack of validation on the user-supplied 'url' parameter. The application performs a GET request to the provided URL without verifying the scheme, host, or destination CIDR. The vulnerability allows for conditional response reflection: valid JSON responses are reflected, while non-JSON responses or connection errors leak specific error messages (e.g., first-byte leaks or TCP timeouts). This can be exploited to perform internal port scanning and access internal-only HTTP services like Kubernetes APIs or metadata endpoints. The issue is fixed in version 1.17.3.

## Affected products

- getarcaneapp Arcane backend <= 1.17.2

## Identifiers

- CVE-2026-40242
- GHSA-ff24-4prj-gpmj
- GO-2026-5356

## Timeline

- 2026-04-10: disclosed
- 2026-04-10: advisory
- 2026-04-10: patched: Fixed in version 1.17.3

## References

- [https://api.github.com/users/msoneri](https://api.github.com/users/msoneri)
- [https://github.com/msoneri](https://github.com/msoneri)
- [https://api.github.com/users/msoneri/gists%7B/gist_id%7D](https://api.github.com/users/msoneri/gists%7B/gist_id%7D)
- [https://api.github.com/users/msoneri/repos](https://api.github.com/users/msoneri/repos)
- [https://avatars.githubusercontent.com/u/40131255?v=4](https://avatars.githubusercontent.com/u/40131255?v=4)
- [https://api.github.com/users/msoneri/events%7B/privacy%7D](https://api.github.com/users/msoneri/events%7B/privacy%7D)

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