kimi-cli · FastMCP: Post-transform component authorization is skipped on direct calls
Affects kimi-cliSource GCVE Database
CVSS 6.8 Medium.
Data as of 26 Oct 2026, 19:42 UTC
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:NWhat to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewkimi-clipkg:brew/kimi-cliOther threats | Affected
| Fixed in– |
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AI-suggested
Upgrading to FastMCP versions 3.4.10 or 4.1.2 or later resolves the issue by enforcing authorization on the final transformed component. Until upgrading, avoid configurations with overlapping proxy templates for protected resources and enforce authorization at the handler or server boundary rather than relying solely on component policies affected by transforms.
Description
FastMCP versions 3.0.0 through 3.4.9 and 4.0.0 through 4.1.1 contain an authorization bypass vulnerability where direct calls to transformed components skip the final authorization check. This allows low-privilege users to invoke protected tools, resources, templates, or prompts that should be denied. The issue arises because the server applies transforms before authorization but does not re-check the authorization on the transformed component in direct lookup paths. Fixes are available in FastMCP 3.4.10 and 4.1.2.
References
- github.com/PrefectHQ/fastmcp/security/advisories/GHSA-7xgj-8392-5q4r (opens in a new tab)
- github.com/PrefectHQ/fastmcp/pull/5933 (opens in a new tab)
- github.com/PrefectHQ/fastmcp/pull/5934 (opens in a new tab)
- github.com/PrefectHQ/fastmcp/commit/85df42fbf2aa631cc81e0f986718b314128e91df (opens in a new tab)
- github.com/PrefectHQ/fastmcp/commit/8649ba5fc91a68568a69729497edeb804a064332 (opens in a new tab)
- github.com/PrefectHQ/fastmcp (opens in a new tab)
- github.com/PrefectHQ/fastmcp/releases/tag/v3.4.10 (opens in a new tab)
- github.com/PrefectHQ/fastmcp/releases/tag/v4.1.2 (opens in a new tab)