chore(deps): update dependency mcp to v1.23.0 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
mcp	==1.19.0 → ==1.23.0

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Model Context Protocol (MCP) Python SDK does not enable DNS rebinding protection by default

CVE-2025-66416 / GHSA-9h52-p55h-vw2f

More information

Details

Description

The Model Context Protocol (MCP) Python SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication using FastMCP with streamable HTTP or SSE transport, and has not configured TransportSecuritySettings, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances.

Note that running HTTP-based MCP servers locally without authentication is not recommended per MCP security best practices. This issue does not affect servers using stdio transport.

Servers created via FastMCP() now have DNS rebinding protection enabled by default when the host parameter is 127.0.0.1 or localhost. Users are advised to update to version 1.23.0 to receive this automatic protection. Users with custom low-level server configurations using StreamableHTTPSessionManager or SseServerTransport directly should explicitly configure TransportSecuritySettings when running an unauthenticated server on localhost.

Severity

• CVSS Score: 7.6 / 10 (High)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

References

• https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-9h52-p55h-vw2f
• https://github.com/modelcontextprotocol/python-sdk/commit/d3a184119e4479ea6a63590bc41f01dc06e3fa99
• https://nvd.nist.gov/vuln/detail/CVE-2025-66416
• https://github.com/advisories/GHSA-9h52-p55h-vw2f

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

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Release Notes

modelcontextprotocol/python-sdk (mcp)

v1.23.0

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Summary

This release brings us up to speed with the latest MCP spec 2025-11-25. Take a look at the latest spec as well as the release blog post.

What's Changed

• Add tests for JSON Schema 2020-12 field preservation (SEP-1613) by @​felixweinberger in #​1649
• Add client_secret_basic authentication support by @​jonshea in #​1334
• Implement SEP-1577 - Sampling With Tools by @​ochafik in #​1594
• SEP-1330: Elicitation Enum Schema Improvements and Standards Compliance by @​chughtapan in #​1246
• [auth][conformance] add conformance auth client by @​pcarleton in #​1640
• Implement SEP-986: Tool name validation by @​felixweinberger in #​1655
• fix: url for spec by @​felixweinberger in #​1659
• feat: implement SEP-991 URL-based client ID (CIMD) support by @​pcarleton in #​1652
• Update doc string on custom_route by @​pcarleton in #​1660
• Implement SEP-1036: URL mode elicitation for secure out-of-band interactions by @​cbcoutinho in #​1580
• Skip empty SSE data to avoid parsing errors by @​felixweinberger in #​1670
• SEP-1686: Tasks by @​maxisbey in #​1645
• Add on_session_created callback option by @​crondinini-ant in #​1710
• Add SSE polling support (SEP-1699) by @​felixweinberger in #​1654
• Support client_credentials flow with JWT and Basic auth by @​pcarleton in #​1663
• feat: backwards-compatible create_message overloads for SEP-1577 by @​felixweinberger in #​1713
• Auto-enable DNS rebinding protection for localhost servers by @​pcarleton (d3a1841)

New Contributors

• @​ochafik made their first contribution in #​1594

Full Changelog: modelcontextprotocol/python-sdk@v1.22.0...v1.23.0

v1.22.0

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What's Changed

• feat: Pass through and expose additional parameters in ClientSessionGroup.call_tool and .connect_to_server by @​inaku-Gyan in #​1576
• chore: Lazy import jsonschema library by @​wuliang229 in #​1596
• docs: Update examples to use stateless HTTP with JSON responses by @​domdomegg in #​1499

New Contributors

• @​wuliang229 made their first contribution in #​1596

Full Changelog: modelcontextprotocol/python-sdk@v1.21.1...v1.22.0

v1.21.2

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Hotfix Release

This is a hotfix release to address a critical bug in OAuth scope handling that caused failures on 401 responses.

Related:

• #​1630
• #​1632

What's Changed

• fix get_client_metadata_scopes on 401 by @​abliznyuk in #​1631

New Contributors

• @​abliznyuk made their first contribution in #​1631

Full Changelog: modelcontextprotocol/python-sdk@v1.21.1...v1.21.2

v1.21.1

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What's Changed

• Add everything-server for comprehensive MCP conformance testing by @​felixweinberger in #​1587
• Get baseline 100% clean coverage by @​maxisbey in #​1553
• Add end-of-file-fixer pre-commit hook by @​maxisbey in #​1610
• Add coverage baseline commit to git-blame-ignore by @​maxisbey in #​1613
• Add SEP-1034 conformance test support to everything-server by @​felixweinberger in #​1604
• refactor: extract OAuth helper functions and simplify provider state by @​maxisbey in #​1586
• Add client_id_metadata_document_supported to OAuthMetadata by @​maxisbey in #​1603
• Fix OAuth discovery fallback and URL ordering by @​maxisbey in #​1624
• Refactor func_metadata() implementation by @​Viicos in #​1496
• Fix CI highest resolution test to actually test highest versions by @​maxisbey in #​1609

New Contributors

• @​Viicos made their first contribution in #​1496

Full Changelog: modelcontextprotocol/python-sdk@v1.21.0...v1.21.1

v1.21.0

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What's Changed

• docs: use article "an" before "MCP" instead of "a" by @​koic in #​1558
• Update Starlette to 0.49.1 in uv.lock by @​ColeMurray in #​1559
• Fix typo in ClientSessionGroup doc string by @​inaku-Gyan in #​1572
• Implement SEP-985: OAuth Protected Resource Metadata discovery fallback by @​cbcoutinho in #​1548
• Add --frozen flag to uv run commands in Claude config by @​maxisbey in #​1583
• Add get_server_capabilities() to ClientSession by @​crondinini-ant in #​1588

New Contributors

• @​koic made their first contribution in #​1558
• @​ColeMurray made their first contribution in #​1559
• @​inaku-Gyan made their first contribution in #​1572
• @​cbcoutinho made their first contribution in #​1548
• @​crondinini-ant made their first contribution in #​1588

Full Changelog: modelcontextprotocol/python-sdk@v1.20.0...v1.21.0

v1.20.0

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What's Changed

• Relax Accept header requirement for JSON-only responses by @​domdomegg in #​1500
• fix: replace deprecated dev-dependencies in examples/clients by @​yukuanj in #​1518
• fix: Update spec links to new modelcontextprotocol.io location by @​maxisbey in #​1491
• fix: Replace fixed sleep with active server readiness check in SSE tests by @​maxisbey in #​1526
• fix: Replace arbitrary sleeps with active server readiness checks in tests by @​maxisbey in #​1527
• Fix flaky timeout test in test_88_random_error by @​maxisbey in #​1525
• fix: Replace remaining manual server polling with wait_for_server helper by @​maxisbey in #​1529
• Implement RFC 7523 JWT flows by @​LucaButBoring in #​1247
• Fix pyright error and replace wildcard import with explicit imports by @​maxisbey in #​1532
• Fix auth client example URL handling for oauth provider by @​pcarleton in #​1549

New Contributors

• @​domdomegg made their first contribution in #​1500
• @​pcarleton made their first contribution in #​1549

Full Changelog: modelcontextprotocol/python-sdk@v1.19.0...v1.20.0

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