# 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.

- **Severity:** High 7.6 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** BIT-seaweedfs-2026-77368, GHSA-99q7-x53r-6j4g, MINI-2xqh-mc9j-qm78

## 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 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-77368?

1 open source package ship an affected version, including seaweedfs.


| Package | Ecosystem | 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.

## Is CVE-2026-77368 being exploited?

There is no known exploitation of CVE-2026-77368 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77368 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-77368 in the wild and no public exploit code.

Affected packages and fixed versions:
- seaweedfs (Bitnami): affected from 4.39.0; fixed in 4.40.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77368/ (Markdown: https://insights.sbomify.com/CVE-2026-77368/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77368
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77368
- OSV: https://osv.dev/vulnerability/CVE-2026-77368

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77368/
Summaries are generated and may contain mistakes; the official description above is the record.