CVE-2026-63118

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...

CVE-2026-63119

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StdioTransport and MCP::Client::Stdio in the mcp gem use IOgets without a byte limit, allowing a peer that sends data without a newline to exhaust process memory. This...

CVE-2026-67432

CVE-2026-67432 affects the MCP Ruby SDK before version 0.23.0. The vulnerability exists in MCP::Server::Transports::StreamableHTTPTransport of the mcp gem, which reads and parses an entire JSON-RPC POST body without a size limit, allowing an unauthenticated remote attacker to exhaust memory on th...

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-2026-67431 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-2026-63119 MCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StdioTransport and MCP::Client::Stdio in the mcp gem use IOgets without a byte limit, allowing a peer that sends data without a newline to exhaust process memory. This...

CVE-2026-63119

The CVE affects the MCP Ruby SDK (mcp gem), specifically MCP::Server::Transports::StdioTransport and MCP::Client::Stdio. The vulnerability arises from using IO#gets without a byte limit, allowing an attacker to send data without a newline and trigger unbounded line buffering, causing memory exhau...

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...

USN-8624-1 ruby-sinatra vulnerability

It was discovered that Sinatra did not properly handle header parsing, causing ETag generation to hang when given specific input. A remote attacker could possibly use this issue to cause a denial of service...

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...

CVE-2026-63118

The MCP Ruby SDK (mcp gem) contains a DNS rebind vulnerability in MCP::Server::Transports::StreamableHTTPTransport where HTTP Host/Origin are not validated. This allows a malicious page to bind a victim’s locally running MCP server to a loopback/ LAN address and post JSON‑RPC requests to exposed ...

Low: Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

An update for Red Hat Hardened Images RPMs is now available. This update includes the following RPMs: ruby4.0: ruby4.0-4.0.6-37.1.hum1 aarch64, x8664 ruby4.0-bundled-gems-4.0.6-37.1.hum1 aarch64, x8664 ruby4.0-default-gems-4.0.6-37.1.hum1 noarch ruby4.0-devel-4.0.6-37.1.hum1 aarch64, x8664...

json: Ruby JSON: Denial of service via heap buffer overflow with oversized streamed objects

A flaw was found in Ruby JSON. A remote attacker could exploit a heap buffer overflow vulnerability by providing an oversized streamed object containing a specially crafted string. This could lead to a reliable process crash, resulting in a denial of service DoS for the affected system...

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...

Linux Distros Unpatched Vulnerability : CVE-2026-54619

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available. - sqlite3 provides Ruby bindings for the SQLite3 embedded database. In version 2.9.4 and earlier, redefining a SQLite function with a different arity frees the...

Linux Distros Unpatched Vulnerability : CVE-2026-54603

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available. - OAuth2 is a Ruby wrapper for the OAuth 2.0 and 2.1 authorization frameworks, including OpenID Connect OIDC. From 0.4.0 to 2.0.21, a protocol-relative redirect...

PT-2026-65888

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 fails to validate the HTTP Host or Origin request headers. This allows a malicious browser page to utilize DNS rebinding—a...