CVE-2026-77368 SeaweedFS: Authenticated Cross-Prefix IDOR in Filer TUS Handler Enables Arbitrary Write to Tenant-Forbidden Paths
Authenticated tenants can hijack upload sessions to write or read files in paths forbidden by their JWT prefix restrictions.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-77368?
CVE-2026-77368 is a high-severity missing authorization vulnerability in seaweedfs, published on 26 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
SeaweedFS is a distributed storage system for files and blobs. In version 4.39, the filer's TUS resumable-upload handler checks JWT allowed_prefixes scoping only when a session is created, letting a low-privilege tenant hijack another tenant's upload session to write content to filer paths their own token forbids. The HEAD, PATCH, and DELETE verbs that act on an existing session by its id never verify that the session's stored target path falls within the caller's allowed prefixes, so a tenant who obtains another upload's session identifier can PATCH attacker bytes into it and, on completion, have the file land at the victim's out-of-scope path. The same token can also DELETE other tenants' sessions and HEAD them to read upload progress and size, defeating the JWT prefix isolation. This vulnerability only affects deployments that configure filer JWT signing and have TUS uploads enabled. This issue is fixed in version 4.40.
Weakness: CWE-639
Which versions are affected by CVE-2026-77368?
1 open source package ship an affected version, including seaweedfs.
| Package | Affected | Fixed in |
|---|---|---|
seaweedfs Bitnami | From 4.39.0 | 4.40.0 |
How do I fix CVE-2026-77368?
Upgrade seaweedfs to 4.40.0 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-77368 being exploited?
There is no known exploitation of CVE-2026-77368 in the wild and no public exploit code.
Sources
Also known as BIT-seaweedfs-2026-77368, GHSA-99q7-x53r-6j4g, MINI-2xqh-mc9j-qm78.