Arcane has Unauthenticated SSRF with Conditional Response Reflection in Template Fetch Endpoint
Exact source revision recorded 24 Oct 2026 13:19:41 UTC. It does not establish the source's current position. Latest evidence.
osv · GHSA-ff24-4prj-gpmj
Published### Summary 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. ### Details - No allowlist or denylist of destination hosts/CIDRs - No requirement for the caller to be authenticated Response handling produces four distinct outcomes observable by the caller: - Valid JSON targets return a fully reflected response body if the returned fields fit the expected internal struct - Non-JSON HTTP 200 responses produce an error leaking the first byte of the response (`"Invalid JSON response: invalid character '<'..."`) - Non-200 responses leak the HTTP status code - TCP-level failures distinguish between closed ports (`"connection refused"`) and filtered ones (`"i/o timeout"`) ### PoC Send an unauthenticated GET request to `/api/templates/fetch`, passing the target URL as the `url` query parameter. <img width="1041" height="375" alt="image" src="https://github.com/user-attachments/assets/f9fd475e-90b0-4dec-95e1-0af6263f5bb5" /> ### Impact - Unauthenticated port scanning of internal networks - Access to internal HTTP services not exposed to the public internet (service discovery endpoints, internal dashboards, Kubernetes API)
- Source published
- 10 Apr 2026 20:59:27 UTC
- Source modified
- 21 Jul 2026 14:02:57 UTC
- Observed here
- 24 Oct 2026 13:19:41 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.
CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Publisher rating · HIGH