Executive brief
Sub2API is an API gateway platform that manages quotas for AI service subscriptions by pooling shared upstream account credentials. Authenticated tenants could exploit a path traversal vulnerability to redirect API requests to arbitrary endpoints using the operator's shared authentication credentials, potentially exposing data or accessing unintended services. The vulnerability affects versions 0.1.135 through 0.1.168 and is patched in 0.1.169.
Technical details
The vulnerability is a path traversal flaw in the POST /responses/*subpath wildcard route handler. The gateway spliced client-supplied subpath segments directly into upstream request URLs without validation, allowing authenticated attackers to inject path traversal sequences (e.g., `../`) that alter the URL structure. An authenticated tenant could send requests to arbitrary upstream endpoints using the platform's pooled provider account credentials (OAuth tokens, API keys). The root cause is insufficient input validation of URL path segments before string concatenation. The fix (version 0.1.169) introduces upstream_path_guard.go with a whitelist-based validation scheme that only allows safe characters (word characters, hyphens, periods) and rejects traversal attempts. Authentication is required to exploit this vulnerability; network access is assumed.
Affected products
- Sub2API Sub2API 0.1.135 to 0.1.168
Timeline
- 2026-08-11: disclosed
- 2026-07-31: patched: Fix committed to main branch; version 0.1.169 includes patch