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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.1 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-72921: 0.43% estimated exploitation activity in the next 30 days; percentile 36.95 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact When a filer JWT restricts a token to a set of path prefixes via allowedprefixes, 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 allowedprefixes 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/filerserverhandlers.go (JWT allowedprefixes 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…

Published by the source

2 Sep 2026, 23:42 UTC

Last modified by the source

10 Sep 2026, 15:25 UTC

Source last checked

26 Oct 2026, 15:28 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-gv5w-hfx8-8cwq

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6361

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-gv5w-hfx8-8cwq

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# Patch Next advisory brief: CVE-2026-72921

Advisory: SeaweedFS: Filer JWT allowed_prefixes literal prefix match allows cross-tenant access to sibling paths
IDs: CVE-2026-72921, GHSA-gv5w-hfx8-8cwq
Record: https://patchnext.com/advisories/cve-2026-72921 (revision 3, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/seaweedfs/seaweedfs 0.0.0-20260512171048-05ed5c9ae8a2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/seaweedfs/seaweedfs: affected < 0.0.0-20260512171048-05ed5c9ae8a2; fixed in 0.0.0-20260512171048-05ed5c9ae8a2

## Suggested inspection (read-only)
- Go github.com/seaweedfs/seaweedfs: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/seaweedfs/seaweedfs.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-gv5w-hfx8-8cwq (OSV record GHSA-gv5w-hfx8-8cwq lists affected ranges: Go github.com/seaweedfs/seaweedfs >=0 <0.0.0-20260512171048-05ed5c9ae8a2 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6361 (OSV record GO-2026-6361 lists affected ranges: Go github.com/seaweedfs/seaweedfs >=0 <0.0.0-20260512171048-05ed5c9ae8a2 (fixed))
- Verified: https://github.com/advisories/GHSA-gv5w-hfx8-8cwq (GitHub-reviewed advisory GHSA-gv5w-hfx8-8cwq lists affected ranges: Go github.com/seaweedfs/seaweedfs >=0 <0.0.0-20260512171048-05ed5c9ae8a2)

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