CVE-2026-73079 in Sub2API
Summary
by MITRE • 08/11/2026
Sub2API is an AI API gateway platform designed to distribute and manage API quotas from AI product subscriptions. From 0.1.135, to 0.1.168, platform API keys issued to tenants are exchanged for upstream requests made with shared provider accounts (ChatGPT/Codex OAuth, OpenAI platform keys, or an operator-configured base URL) that belong to the operator, not to the caller. The `POST /responses/*subpath` wildcard routes spliced the client-supplied subpath into the upstream URL with no validation. This lets an authenticated tenant relay requests to arbitrary upstream endpoints using pooled account credentials via a path traversal. This vulnerability is fixed in 0.1.169.
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Analysis
by VulDB Data Team • 08/11/2026
The Sub2API platform represents a sophisticated AI API gateway solution that serves as an intermediary between tenants and various AI service providers including ChatGPT, Codex, and OpenAI platforms. This system operates by managing API quotas and distributing access to subscription-based AI services while maintaining a shared infrastructure model where operator-owned credentials are pooled for upstream requests. The vulnerability analysis reveals a critical design flaw in the platform's authentication and request routing mechanisms that fundamentally undermines the security boundaries between tenants and the underlying service providers.
The technical implementation of this vulnerability stems from improper input validation within the POST /responses/*subpath wildcard route handling system. When authenticated tenants make requests through this endpoint, the platform performs no validation on the client-supplied subpath parameter before incorporating it into the upstream URL construction process. This creates a classic path traversal vulnerability where an attacker can manipulate the request path to redirect traffic to arbitrary upstream endpoints. The flaw specifically manifests in how the system exchanges tenant API keys for operator-owned credentials during upstream requests, creating a scenario where any authenticated user can leverage shared provider accounts to access unauthorized resources.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential data leakage and unauthorized access to premium AI services. An attacker could exploit this weakness to make requests to endpoints that should be restricted to specific tenants or service providers, potentially accessing sensitive information or consuming API quotas that belong to other users. The vulnerability allows for the exploitation of pooled operator credentials across multiple tenants, creating a scenario where one compromised tenant could potentially access resources belonging to other users within the same organization or platform. This represents a significant breach of the principle of least privilege and could lead to unauthorized consumption of expensive AI service credits.
The security implications align with CWE-22 Path Traversal and CWE-352 Cross-Site Request Forgery patterns, where insufficient input validation leads to unauthorized access to resources. From an attack perspective, this vulnerability maps to ATT&CK technique T1566.001 Valid Accounts, as it leverages legitimate authenticated tenant credentials to perform unauthorized actions against upstream services. The fix implemented in version 0.1.169 demonstrates proper input sanitization and validation of the subpath parameter before incorporating it into upstream request construction. This remediation approach follows security best practices by ensuring that all user-supplied input undergoes rigorous validation before being used in critical system operations, preventing the injection of malicious paths that could lead to unauthorized access.
Organizations utilizing Sub2API platforms should immediately implement the updated version 0.1.169 and conduct comprehensive audits of their tenant access controls and credential management systems. The vulnerability highlights the importance of proper input validation in API gateway implementations and demonstrates how seemingly benign routing mechanisms can create significant security risks when combined with shared credential models. Security teams must also consider implementing additional monitoring for unusual patterns in upstream API usage that might indicate exploitation attempts, as this vulnerability could enable attackers to consume quotas without detection while potentially accessing unauthorized resources through the shared operator credentials infrastructure.