googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)

NGHIÊM TRỌNG 9.1CVE-2026-11718 · GHSA-wcpr-6g7x-p44r · GO-2026-5706 · Công bố 18/06/2026 · cập nhật 26/10/2026

Tóm tắt nhanh

CVE-2026-11718 là lỗ hổng mức NGHIÊM TRỌNG (CVSS 9.1) ảnh hưởng github.com/googleapis/mcp-toolbox, mcp toolbox for databases (google).
Xác suất bị khai thác trong 30 ngày tới (EPSS): 0.18%, cao hơn 8.1% các lỗ hổng khác.
Cách xử lý: cập nhật lên 1.4.0 hoặc mới hơn.

Gói / sản phẩm	Phiên bản bị ảnh hưởng	Phiên bản đã vá
github.com/googleapis/mcp-toolbox Go	`< 1.4.0`	`1.4.0`
mcp toolbox for databases google	`≥ 1.0.0, ≤ 1.3.0`	Chưa có bản vá

Mô tả

An authentication bypass vulnerability exists in the generic opaque token validation path (validateOpaqueToken) of googleapis/mcp-toolbox.

When the toolbox validates an opaque token via an OAuth 2.0 introspection endpoint (RFC 7662), it decodes the response into an introspectResp struct. However, the subsequent claim-checking logic (validateClaims) evaluates the issuer condition as if a.issuer != "" && iss != "". If the external OAuth provider's introspection response omits the optional iss (issuer) field completely, the variable iss defaults to an empty string. This causes the conditional block to evaluate to false and be skipped silently. Consequently, the application accepts tokens issued by unauthorized or unintended third-party identity providers.

Mô tả của NVD

An authentication bypass vulnerability exists in the generic opaque token validation path (validateOpaqueToken) of googleapis/mcp-toolbox. When the toolbox validates an opaque token via an OAuth 2.0 introspection endpoint (RFC 7662), it decodes the response into an introspectResp struct. However, the subsequent claim-checking logic (validateClaims) evaluates the issuer condition as if a.issuer != "" && iss != "". If the external OAuth provider's introspection response omits the optional iss (issuer) field completely, the variable iss defaults to an empty string. This causes the conditional block to evaluate to false and be skipped silently. Consequently, the application accepts tokens issued by unauthorized or unintended third-party identity providers.