The Model Context Protocol’s maintainers have adopted a fixed release calendar, with spec releases every March and September, according to a monthly report by the web agency eSEOspace. The change moves the release that had been planned for December 2026 to late March 2027.
MCP is the open standard many AI agents use to connect to outside tools and data. The report, written by Irina Shvaya and dated Oct. 28, says it was built from primary sources such as the official spec, registry and GitHub repositories.
The calendar comes from a proposal called SEP-3398, “Release Cycle Updates.” The report says it was accepted on Oct. 14, and GitHub shows the pull request merged on Oct. 27.
Its summary on GitHub describes March and September releases, overlapping eight-month cycles, rotating release managers and a shared review queue for proposals, “with a proposed transition to March 2027.” The report quotes the proposal as saying releases will happen “generally on the last Tuesday of March and September.”
No new spec version shipped in October. The latest is still dated July 28, 2026, according to the report.
Server Cards and other changes
The Server Cards proposal, SEP-2127, was merged as final on Oct. 6, the report says. A Server Card is a small metadata file describing a remote MCP server, such as its supported protocol versions and how to connect. The report says it uses a .well-known/ai-catalog.json address so an app can learn about a server before connecting.
The maintainers also formed a Tasks and Events Working Group on Oct. 20 and turned the Agents Working Group into an interest group, according to the report. On Oct. 5 the project added a guide on local server security, which notes that the stdio transport, the standard way to run a server on your own machine, “is not a sandbox.”
eSEOspace counted 52,141 servers in the official MCP Registry on Oct. 28, with 66% offering a hosted endpoint. Those are the agency’s own counts, and it notes the registry doesn’t vet code.
A busy month for security
The official MCP GitHub repositories published 31 security advisories between Oct. 1 and Oct. 28, according to the report: two rated critical, 10 high, 14 medium and five low. eSEOspace says it counted them through the GitHub API.
Both critical advisories were in MCP Inspector, a tool for testing MCP servers. The report quotes one as saying a “Remote MCP App can steal proxy auth token and execute arbitrary local commands,” affecting versions 0.20.0 to 1.0.2. It advises updating MCP Inspector to version 1.0.3 or later.
Other advisories covered the reference servers and the TypeScript, Java, Python and Rust software development kits. In one TypeScript case, shared server instances could deliver one client’s messages to another, the report says. eSEOspace says most fixes involved known patterns like resource exhaustion and OAuth mistakes, and that SDK teams spent October adding limits on request sizes, session counts and memory.
Outside the protocol, the hosting company Smithery said it would shut down its hosted connection services on Oct. 31, keeping its directory online powered by Arcade.dev, the report says. It advises anyone calling a Smithery-hosted server address to switch to the vendor’s own address.
AgenticFeed checked the release calendar proposal on GitHub. The report’s other figures are eSEOspace’s own counts.
Source: eSEOspace – State of MCP: October 2026, Irina Shvaya, “State of MCP: October 2026”
Additional sources: GitHub (modelcontextprotocol), Model Context Protocol maintainers, “SEP-3398: Release Cycle Updates”
