{"data":{"id":"ac58c5f1-e76f-428f-9fbe-2418d2c0f47d","title":"GHSA-7xgj-8392-5q4r: FastMCP: Post-transform component authorization is skipped on direct calls","summary":"FastMCP versions 3.0.0 through 3.4.9 and 4.0.0 through 4.1.1 skip the final authorization check on direct component lookups when a server transform changes the component's metadata. A low-privilege client that knows the transformed component name can invoke a tool or retrieve a resource or prompt that the configured policy denies. A denied concrete resource also shadows a matching proxy template at its URI.","solution":"Fixed in FastMCP 3.4.10 and 4.1.2. Until upgrading, avoid overlapping proxy templates for protected resources and enforce the required authorization at the handler or server boundary rather than relying on a policy whose inputs are changed by a transform.","labels":["security"],"sourceUrl":"https://github.com/advisories/GHSA-7xgj-8392-5q4r","publishedAt":"2026-10-23T21:32:06.000Z","cveId":null,"cweIds":null,"cvssScore":null,"cvssSeverity":"medium","severity":"medium","attackType":["other"],"issueType":"vulnerability","affectedPackages":["fastmcp-slim@>= 4.0.0, < 4.1.2 (fixed: 4.1.2)","fastmcp-slim@>= 3.0.0, < 3.4.10 (fixed: 3.4.10)","fastmcp@>= 4.0.0, < 4.1.2 (fixed: 4.1.2)","fastmcp@>= 3.0.0, < 3.4.10 (fixed: 3.4.10)"],"affectedPackageNames":["fastmcp-slim","fastmcp"],"affectedPackageRefs":["pypi:fastmcp-slim","pypi:fastmcp"],"affectedVendors":[],"affectedVendorsRaw":["FastMCP"],"classifierModel":"claude-haiku-5-5","classifierPromptVersion":"v4","summaryPromptVersion":"v2","headline":null,"headlinePromptVersion":null,"cvssVector":null,"attackVector":null,"attackComplexity":null,"privilegesRequired":null,"userInteraction":null,"exploitMaturity":null,"epssScore":null,"epssCheckedAt":null,"kevDateAdded":null,"advisoryAliases":["GHSA-7xgj-8392-5q4r"],"affectedPackagesSource":null,"affectedPackagesCheckedAt":null,"patchAvailable":true,"disclosureDate":"2026-10-23T21:32:06.000Z","capecIds":null,"crossRefCount":0,"attackSophistication":"trivial","impactType":["confidentiality","integrity"],"aiComponentTargeted":"plugin","llmSpecific":false,"classifierConfidence":0.9,"researchCategory":null,"atlasIds":null}}