What happened
NVD published this CVSS 7.7 High vulnerability on Sept 16, 2026 affecting Kong's JWT signature verification specifically in the context of MCP OAuth2 and DataKit integrations within Kong API Gateway Enterprise.
Why it matters
As enterprises route AI-agent-to-tool traffic through API gateways like Kong for MCP authentication and rate control, a JWT algorithm-confusion bypass in that exact validation path lets an attacker forge tokens to invoke privileged MCP tools without valid credentials, defeating the primary authentication control protecting agentic tool access at scale.
Attack vector
The affected JWT validation code fails to verify that the token's signing algorithm is compatible with the verification key type, enabling an algorithm-confusion attack (e.g. RS256/HS256 confusion) to forge valid-looking JWTs and bypass authentication for MCP OAuth2-protected tool calls or DataKit integrations.
Affected systems
Kong API Gateway Enterprise (MCP OAuth2 / DataKit JWT validation components)
Mitigation
Apply Kong's patch per the gateway changelog; explicitly pin and enforce expected signing algorithms in JWT verification configuration rather than trusting the algorithm declared in the token header.