fix: validate_scope treats None registered scopes as no restrictions#2224
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fix: validate_scope treats None registered scopes as no restrictions#2224shivama205 wants to merge 2 commits into
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When a client was registered without specific scopes (scope=None), validate_scope() converted None to an empty list, causing all requested scopes to be rejected with InvalidScopeError. Now None is correctly treated as "no restrictions", allowing any scope. Closes modelcontextprotocol#2216
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maxisbey
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Jah-yee
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Mar 13, 2026
When self.scope is None (no scopes registered), the validate_scope method incorrectly treated it as an empty allowed list, rejecting all requested scopes with InvalidScopeError. Now None is correctly treated as 'no restrictions', allowing any requested scope through. Fixes modelcontextprotocol#2216 Closes modelcontextprotocol#2224
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Closing — superseded by #2301, which removes the registration-scope check entirely (it breaks the spec's step-up authorization flow). Thanks for the analysis on the issue, which fed into that direction. |
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Summary
OAuthClientMetadata.validate_scope()incorrectly treatedself.scope = None(no scopes registered) as an empty allowed list, rejecting all requested scopes withInvalidScopeErrorNoneis correctly treated as "no restrictions", allowing any requested scope throughCloses #2216
Changes
src/mcp/shared/auth.py— early return whenself.scope is Noneinstead of converting to empty listtests/shared/test_auth.py— added 6 unit tests forvalidate_scopecovering None/matching/rejection/empty casesTest plan
test_authorize_invalid_scope)ruff checkpassesruff formatpassespyrightpasses with 0 errors