MCP Ruby SDK: Ruby SSE Session Poisoning

Summary Vulnerability: Missing Session Ownership Validation in the Ruby MCP SDK's Streamable and SSE HTTP transport implementation. Any attacker with a stolen session ID can execute tools with the victim's session. This is a silent attack - the victim's session is compromised and being used for...

GHSA-H669-8M4G-R2HC MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport

Summary An unauthenticated remote attacker can force any MCP Ruby SDK server using MCP::Server::Transports::StreamableHTTPTransport to allocate gigabytes of memory by sending a single oversized JSON-RPC POST. The transport reads the entire HTTP body into a Ruby String and parses it with...

MCP Ruby SDK: Streamable HTTP transport lacks DNS-rebinding (Host/Origin) protection

Summary MCP::Server::Transports::StreamableHTTPTransport the Rack-mountable Streamable HTTP transport in the mcp gem processes every incoming JSON-RPC request without ever inspecting the HTTP Host or Origin request headers. There is no AllowedHosts/AllowedOrigins allowlist and no DNS-rebinding...

CVE-2026-67432 MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem reads and parses an entire JSON-RPC POST body without a size limit, allowing an unauthenticated remote attacker to exhaust process...

CVE-2026-67432 MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem reads and parses an entire JSON-RPC POST body without a size limit, allowing an unauthenticated remote attacker to exhaust process...

CVE-2026-67431 MCP Ruby SDK: Ruby SSE Session Poisoning

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not bind a session ID to a session owner, allowing an attacker with a stolen session ID to send tools/call requests that...

CVE-2026-67430

CVE-2026-67430 affects the MCP Ruby SDK (mcp gem) prior to 0.23.0. The vulnerability is in MCP::Server::Transports::StreamableHTTPTransport, which does not expire sessions by default, allowing repeated initialize requests to retain unbounded ServerSession objects and cause memory exhaustion. The ...

CVE-2026-67430 MCP Ruby SDK: Unbounded session retention in StreamableHTTPTransport allows memory exhaustion via initialize flood

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not expire sessions by default, so repeated initialize requests retain unbounded ServerSession objects and can exhaust proces...

CVE-2026-67430

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not expire sessions by default, so repeated initialize requests retain unbounded ServerSession objects and can exhaust proces...

CVE-2026-63118 MCP Ruby SDK: Streamable HTTP transport lacks DNS-rebinding (Host/Origin) protection

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not validate the HTTP Host or Origin request headers, which allows a malicious browser page to use DNS rebinding to reach a...

PT-2026-65899

Name of the Vulnerable Software and Affected Versions mcp versions prior to 0.23.0 Description The MCP::Server::Transports::StreamableHTTPTransport component in the mcp gem reads and parses an entire JSON-RPC POST body without enforcing a size limit. This allows an unauthenticated remote attacker...

CVE-2026-16496

The terraform-mcp-server before version 1.1.0 is vulnerable to an authorization bypass in the streamable-HTTP stateful transport mode that may allow a user who obtains another user's MCP session ID to have their tool calls executed using that user's Terraform credentials. This vulnerability,...

CVE-2026-16498

The terraform-mcp-server before version 1.1.0 is vulnerable to a cross-tenant credential reuse issue in the streamable-HTTP stateless transport mode that may allow one user's Terraform token to be used to execute tool calls on behalf of subsequent users. This vulnerability, CVE-2026-16498, is fix...

EUVD-2026-49940

The terraform-mcp-server before version 1.1.0 is vulnerable to an authorization bypass in the streamable-HTTP stateful transport mode that may allow a user who obtains another user's MCP session ID to have their tool calls executed using that user's Terraform credentials. This vulnerability,...

CVE-2026-16496 terraform-mcp-server vulnerable to cross-user credential inheritance if an MCP session ID is obtained by another user

The terraform-mcp-server before version 1.1.0 is vulnerable to an authorization bypass in the streamable-HTTP stateful transport mode that may allow a user who obtains another user's MCP session ID to have their tool calls executed using that user's Terraform credentials. This vulnerability,...

Multiple vulnerabilities impacting HashiCorp Terraform MCP Server

Summary The terraform-mcp-server before version 1.1.0 is vulnerable to three related issues in its streamable-HTTP transport: a server-side request forgery issue that may allow an unauthenticated client to redirect the server’s bearer token to an attacker-controlled endpoint CVE-2026-14869, an...

PT-2026-65551

Name of the Vulnerable Software and Affected Versions terraform-mcp-server versions prior to 1.1.0 Description A cross-tenant credential reuse issue exists in the streamable-HTTP stateless transport mode. This flaw may allow a Terraform token belonging to one user to be reused to execute tool cal...

PYSEC-2026-3482 MCP Python SDK: HTTP transports serve session requests without verifying the authenticated principal

Summary In affected versions, the SSE and Streamable HTTP server transports routed incoming requests to an existing session based only on the session identifier, without verifying that the request was authenticated as the same principal that created the session. Anyone who learned or guessed a...

PT-2026-64095

Server-Side Request Forgery SSRF in upload ad image via Unrestricted image url Fetch Summary The upload ad image MCP tool in meta-ads-mcp v1.0.113 passes an attacker-controlled image url parameter directly to an HTTP fetch helper httpx.AsyncClientfollow redirects=True.geturl without any scheme,...

meta-ads-mcp: Server-Side Request Forgery (SSRF) in `upload_ad_image` via Unrestricted `image_url` Fetch

Server-Side Request Forgery SSRF in uploadadimage via Unrestricted imageurl Fetch Summary The uploadadimage MCP tool in meta-ads-mcp v1.0.113 passes an attacker-controlled imageurl parameter directly to an HTTP fetch helper httpx.AsyncClientfollowredirects=True.geturl without any scheme, host, or...