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2 actionable advisories, newest first. Withdrawn advisories and news are excluded. Coverage is partial.
Maintainer assessment and remediation This report is accepted as a FastMCP authorization vulnerability. In supported configurations, a server transform can change the metadata used by a component's authorization policy. Direct lookups previously checked the original component but returned the transformed component without rechecking its policy. A client that knows the component identifier can invoke a tool or retrieve a resource or prompt that the configured policy denies. The fixes authorize the final transformed tools, resources, templates, and prompts. A denied concrete resource also shadows a matching resource template at its URI, preventing proxy templates from retrieving the same protected resource upstream. Authorized callers, authorized component versions, and templates for genuinely absent concrete resources remain supported. Affected stable release lines: FastMCP 3.0.0–3.4.9 and 4.0.0–4.1.1. The missing final authorization check is present in v3.0.0 history and was…
Recommended action: Upgrade to 4.1.2 or 3.4.10 by release line, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.
Maintainer assessment and remediation This report is accepted as a FastMCP credential-binding vulnerability. Affected versions of the OAuth client credentials providers do not expose the authorization-server issuer that owns pre-registered credentials. An untrusted or compromised MCP server can therefore advertise a different authorization server and receive the client secret or a signed assertion. Signing keys themselves remain local; assertion replayability depends on the assertion source and audience policy. Affected stable versions are 4.0.0–4.1.1 of fastmcp and fastmcp-slim. The wrappers were introduced in 4.0.0a1; 3.x does not include them. The 4.1.2 fix adds issuer to ClientCredentialsOAuthProvider and PrivateKeyJWTOAuthProvider and requires MCP SDK 2.2.0. It also discards refresh credentials from reloaded tokens: without persisted authorization-server metadata, inherited refresh could otherwise transmit credentials before issuer discovery, including when a cached token was…
Recommended action: Upgrade to 4.1.2 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.