File Browser: Colliding username normalization gives two users the same home directory

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-62685: 0.55% estimated exploitation activity in the next 30 days; percentile 46.22 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary FileBrowser confines each user to a scope: a home directory that acts as the boundary for everything they can read or write. When self-registration and automatic home-directory creation are both enabled (Signup=true and CreateUserDir=true), a new user's scope is built from their username after it passes through cleanUsername(). That function rewrites the name: it strips .. and replaces every character outside 0-9A-Za-z@\-. with -. The problem is that this rewrite is many-to-one: different usernames can produce the same result, and FileBrowser never checks whether the resulting scope is already taken. So team/one, team one, and team-one all collapse to the same directory name, and whoever registers second is handed the same home directory as the first user instead of an isolated one. This breaks per-user isolation. An attacker can pick a username that normalizes onto a victim's directory (for example registering alice/ or al..ice to land in alice's home) and gain full read and…

Published by the source

20 Jul 2026, 22:19 UTC

Last modified by the source

20 Jul 2026, 22:19 UTC

Source last checked

26 Oct 2026, 15:25 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-7rc3-g7h6-22m7

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-62685

Advisory: File Browser: Colliding username normalization gives two users the same home directory
IDs: CVE-2026-62685, GHSA-7rc3-g7h6-22m7
Record: https://patchnext.com/advisories/cve-2026-62685 (revision 1, source checked 26 Oct 2026, 15:25 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/filebrowser/filebrowser/v2 2.63.17. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/filebrowser/filebrowser/v2: affected <= 2.63.16; fixed in 2.63.17

## Suggested inspection (read-only)
- Go github.com/filebrowser/filebrowser/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/filebrowser/filebrowser/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-7rc3-g7h6-22m7 (GitHub-reviewed advisory GHSA-7rc3-g7h6-22m7 lists affected ranges: Go github.com/filebrowser/filebrowser/v2 >=0 <=2.63.16)

Commands are suggestions: review each one before running it.