CVE-2026-32759 File Browser TUS Negative Upload-Length Fires Post-Upload Hooks Prematurely
Authenticated users can trigger premature upload completion via negative length, enabling DoS or command execution if exec hooks are enabled.
- 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-2026-32759?
CVE-2026-32759 is a medium-severity vulnerability in filebrowser, published on 19 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. In versions on the 2.x branch prior to 2.33.8, the TUS resumable upload handler parses the Upload-Length header as a signed 64-bit integer without validating that the value is non-negative, allowing an authenticated user to supply a negative value that instantly satisfies the upload completion condition upon the first PATCH request. This causes the server to fire after_upload exec hooks with empty or partial files, enabling an attacker to repeatedly trigger any configured hook with arbitrary filenames and zero bytes written. The impact ranges from DoS through expensive processing hooks, to command injection amplification when combined with malicious filenames, to abuse of upload-driven workflows like S3 ingestion or database inserts. Even without exec hooks enabled, the negative Upload-Length creates inconsistent cache entries where files are marked complete but contain no data. All deployments using the TUS upload endpoint (/api/tus) are affected, with the enableExec flag escalating the impact from cache inconsistency to remote command execution. This feature has been disabled by default for all installations from v2.33.8 onwards, including for existent installations. To exploit this vulnerability, the instance administrator must turn on a feature and ignore all the warnings about known vulnerabilities.
Weakness: CWE-190
Which versions are affected by CVE-2026-32759?
4 open source packages ship an affected version, including github.com/filebrowser/filebrowser/v2 and github.com/filebrowser/filebrowser. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/filebrowser/filebrowser/v2 Go | All versions | None |
github.com/filebrowser/filebrowser/v2 Go | All versions | 2.33.8 |
github.com/filebrowser/filebrowser/v2 Go | All versions | 2.33.8 |
github.com/filebrowser/filebrowser Go | All versions | None |
Products include Filebrowser Filebrowser.
How do I fix CVE-2026-32759?
Upgrade github.com/filebrowser/filebrowser/v2 to 2.33.8 or later.
Is CVE-2026-32759 being exploited?
There is no known exploitation of CVE-2026-32759 in the wild and no public exploit code.
Other vulnerabilities in filebrowser
- CVE-2026-32760 File Browser Self Registration Grants Any User Admin Access When Default Permissions Include Admin
- CVE-2026-29188 File Browser: TUS Delete Endpoint Bypasses Delete Permission Check
- CVE-2023-39612 Cross-site scripting in n/a
- CVE-2026-30934 FileBrowser Quantum: Stored XSS in public share page via unsanitized share metadata (text/template misuse)
- CVE-2021-46398 Cross-Site Request Forgery in Filebrowser
Sources
Also known as GHSA-ffx7-75gc-jg7c, GO-2026-4713.