# CVE-2026-77368: SeaweedFS TUS resumable-upload JWT authorization bypass

Source: https://junglewise.ai/threats/cve-2026-77368-seaweedfs-tus-resumable-upload-jwt-authorization-bypass  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-26. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-77368 · Severity: high · CVSS 7.6 · Published 2026-08-26

SeaweedFS is a distributed storage system used to store and manage files and blobs across multiple nodes. In version 4.39, a multi-tenant deployment using JWT token scoping can be exploited by a low-privilege tenant to hijack other tenants' file uploads, write content to forbidden storage paths, read upload progress, and delete other users' sessions—compromising data isolation and potentially leading to unauthorized file placement or data loss.

Technologies: [SeaweedFS](https://junglewise.ai/threats/technologies/seaweedfs). Vendors: [SeaweedFS](https://junglewise.ai/threats/vendors/seaweedfs).

## Quick answers

**Is CVE-2026-77368 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77368 being exploited in the wild.

**How severe is CVE-2026-77368?** High severity, with a CVSS score of 7.6, published 26 August 2026.

**Which products and versions are affected?** SeaweedFS 4.39.

**Is there a fix for CVE-2026-77368?** A patch was published on 2026-07-10: Fix commits merged; version 4.40 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-77368 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-77368?** Check whether you run SeaweedFS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an authorization bypass in the TUS (Tus Resumable Upload Protocol) handler. The filer's JWT scope check (allowed_prefixes) is only enforced when a new upload session is created (POST), but the HEAD, PATCH, and DELETE operations that manipulate existing sessions by session ID do not verify that the session's stored target path falls within the caller's allowed prefixes. A low-privilege tenant who learns another tenant's session ID (which, while unguessable to unauthenticated users, is not an authorization boundary against legitimate tenants) can modify that session to write attacker-controlled bytes to arbitrary paths, delete other sessions, or read progress metadata. This affects only deployments with JWT signing configured and TUS uploads enabled. The vulnerability was fixed in version 4.40 by validating the session target path on all operations and failing closed when resolution fails.

## Affected products

- SeaweedFS SeaweedFS 4.39

## Timeline

- 2026-08-26: disclosed
- 2026-07-10: patched: Fix commits merged; version 4.40 released

## References

- [https://github.com/seaweedfs/seaweedfs/commit/ce82e3a057080162a9fba11889157d2255815f71](https://github.com/seaweedfs/seaweedfs/commit/ce82e3a057080162a9fba11889157d2255815f71)
- [https://github.com/seaweedfs/seaweedfs/commit/fa549e9c83b7799d512157d728f52052912831af](https://github.com/seaweedfs/seaweedfs/commit/fa549e9c83b7799d512157d728f52052912831af)

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