Moderate severityNVD Advisory· Published Jul 29, 2026· Updated Jul 30, 2026
MCP Ruby SDK: Unbounded session retention in StreamableHTTPTransport allows memory exhaustion via initialize flood
CVE-2026-67430
Description
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 process memory. This issue is fixed in version 0.23.0.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
mcpRubyGems | < 0.23.0 | 0.23.0 |
Affected products
2- Range: <0.23.0
- Range: <0.23.0
Patches
Vulnerability mechanics
References
5- github.com/advisories/GHSA-52jp-gj8w-j6xhghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-67430ghsaADVISORY
- github.com/modelcontextprotocol/ruby-sdk/commit/afb968c468c178c4d3294b423fcce250621692f4ghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.23.0ghsax_refsource_MISCWEB
- github.com/modelcontextprotocol/ruby-sdk/security/advisories/GHSA-52jp-gj8w-j6xhghsax_refsource_CONFIRMWEB
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