EUVD-2026-290210

fkie_cve-2026-35605

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to 2.63.1, the Matches() function in rules/rules.go uses strings.HasPrefix() without a trailing directory separator when matching paths against access rules. A rule for /uploads also matches /uploads_backup/, granting or denying access to unintended directories. This vulnerability is fixed in 2.63.1.

GHSA-5q48-q4fm-g3m6 — File Browser has an access rule bypass via HasPrefix without trailing separator in path matching

Affected: Go: github.com/filebrowser/filebrowser/v2

Hi,

The `Matches()` function in `rules/rules.go` uses `strings.HasPrefix()` without a trailing directory separator when matching paths against access rules. A rule for `/uploads` also matches `/uploads_backup/`, granting or denying access to unintended directories. Verified against v2.62.2 (commit 860c19d).

## Details

At `rules/rules.go:29-35`:

func (r *Rule) Matches(path string) bool { if r.Regex { return r.Regexp.MatchString(path) } return strings.HasPrefix(path, r.Path) }

When a rule has `Path: "/uploads"`, any path starting with `/uploads` matches, including `/uploads_backup/secret.txt`. The regex variant at line 31 uses proper matching, but the non-regex path uses a prefix check without ensuring the match ends at a directory boundary.

The `Check()` function at `http/data.go:29-48` iterates all rules with last-match-wins semantics. No secondary validation exists beyond this prefix check.

## PoC

Admin configures: allow rule `Path: "/shared"` for a restricted user.

Filesystem contains: - `/shared/` (intended to be accessible) - `/shared_private/` (intended to be restricted)

User requests `/shared_private/secret.txt`: - `strings.HasPrefix("/shared_private/secret.txt", "/shared")` returns true - Allow rule applies - Access granted to the unintended directory

## Impact

Authenticated users can access files in sibling directories that share a common prefix with an allowed directory, bypassing the admin's intended access co…

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EUVD-2026-290210

fkie_cve-2026-35605

GHSA-5q48-q4fm-g3m6 — File Browser has an access rule bypass via HasPrefix without trailing separator in path matching