Update dependency mcp to v1.23.0 [SECURITY] #3366

renovate · 2025-12-02T21:32:44Z

This PR contains the following updates:

Package	Change	Age	Confidence
mcp	`==1.16.0` -> `==1.23.0`

GitHub Vulnerability Alerts

CVE-2025-66416

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.

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.

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

`v1.19.0`

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What's Changed

feat: add tool metadata in FastMCP.tool decorator by @mat-octave in #1463
Make client examples workspaces to reflect package code by @LucaButBoring in #1466
Expose RequestParams._meta in ClientSession.call_tool by @samchenatti in #1231
Allow CallToolResult to be returned directly to support _meta field for OpenAI Apps by @BrandonShar in #1459
fix: uv CVE-2025-62518 astral-tokio-tar issue GHSA-j5gw-2vrg-8fgx by @cclauss in #1505
fix: use proper dependency resolution in CI by @felixweinberger in #1507
Upgrade GitHub Actions by @cclauss in #1473
test: use errno.ENOENT for command not found assertion by @mingo1996 in #1498
Replace deprecated dev-dependencies with dependency-groups by @yukuanj in #1488
update uv to 0.9.5 by @maxisbey in #1510

New Contributors

@mat-octave made their first contribution in #1463
@samchenatti made their first contribution in #1231
@BrandonShar made their first contribution in #1459
@mingo1996 made their first contribution in #1498

Full Changelog: modelcontextprotocol/python-sdk@v1.18.0...v1.19.0

`v1.18.0`

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What's Changed

[client] Implement MCP OAuth scope selection and step-up authorization by @dogacancolak in #1324
Handles message type Exception in lowlevel/server.py _handle_message function. Mentioned as TODO on line 528. by @AishwaryaKalloli in #786
Fix workspace configuration error with structured_output_lowlevel.py by @felixweinberger in #1471
fix: Remove unnecessary constructor from ResourceServerSettings by @rocky-d in #1424
feat: add resource annotations support to FastMCP by @fennb in #1468
fix: send params as empty object for list methods without cursor by @felixweinberger in #1453
fix: Set the Server session initialization state immediately after respond… by @daamitt in #1478

New Contributors

@dogacancolak made their first contribution in #1324
@rocky-d made their first contribution in #1424
@fennb made their first contribution in #1468
@daamitt made their first contribution in #1478

Full Changelog: modelcontextprotocol/python-sdk@v1.17.0...v1.18.0

`v1.17.0`

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What's Changed

Add documentation structure by @Kludex in #1425
Add documentation about testing by @Kludex in #1426
Improve OAuth protected resource metadata URL construction per RFC 9728 by @shulkx in #1407
feat: add ability to remove tools by @brandonspark in #1322
Update README to link to Python SDK documentation by @felixweinberger in #1430
fix: update CLAUDE.md to remove auto-addition of reviewers. by @felixweinberger in #1431

New Contributors

@shulkx made their first contribution in #1407
@brandonspark made their first contribution in #1322

Full Changelog: modelcontextprotocol/python-sdk@v1.16.0...v1.17.0

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Update dependency mcp to v1.23.0 [SECURITY]

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