SeaweedFS: Filer JWT allowed_prefixes literal prefix match allows cross-tenant access to sibling paths (CVE-2026-72921)
### Impact 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. ### Affected component - `weed/server/filer_server_handlers.go` (JWT `allowed_prefixes` authorization check) ### Patches Fixed in **4.24**. The check now matches on `/`-separated path components after `path.Clean` normalisation, so `/tenant1` authorizes only `/tenant1` and its descendants — not `/tenant1234` or other sibling paths. ### Workarounds Where feasible, choose prefix names that are not string-prefixes of one another (e.g. keep a trailing separator convention). Upgrade to 4.24. ### References - Reported by Kadir Arslan (https://github.com/KadirArslan)
SeaweedFS: Filer JWT allowed_prefixes literal prefix match allows cross-tenant access to sibling paths (CVE-2026-72921)
Description
### Impact 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. ### Affected component - `weed/server/filer_server_handlers.go` (JWT `allowed_prefixes` authorization check) ### Patches Fixed in **4.24**. The check now matches on `/`-separated path components after `path.Clean` normalisation, so `/tenant1` authorizes only `/tenant1` and its descendants — not `/tenant1234` or other sibling paths. ### Workarounds Where feasible, choose prefix names that are not string-prefixes of one another (e.g. keep a trailing separator convention). Upgrade to 4.24. ### References - Reported by Kadir Arslan (https://github.com/KadirArslan)
CVSS v3.1
Score 8.1high
Affected software
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Weaknesses
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-gv5w-hfx8-8cwq
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-72921"]
- Ecosystems
- ["Go"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6a998f69acd9273b49193531
Added to database: 09/03/2026, 15:16:57 UTC
Last updated: 09/04/2026, 00:16:03 UTC
Views: 5
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