CVE-2026-72921: SeaweedFS: Filer JWT allowed_prefixes literal prefix match allows cross-tenant access to sibling paths

When a filer JWT restricts a token to a set of path prefixes via allowed_prefixes, the authorization check used a literal byte-prefix match (strings.HasPrefix). A token scoped to /tenant1 therefore also authorized requests to sibling paths such as /tenant1234, /tenant1-old, and /tenant1backup.

In a multi-tenant deployment this lets the holder of one tenant’s token access another tenant’s data. Because allowed_prefixes gates both read and write tokens, the impact covers cross-tenant reads and writes. A valid scoped token is required, so this is an authorization bypass rather than a fully unauthenticated flaw.