CVE-2026-32758: Github.com/filebrowser/filebrowser/v2 Path Traversal Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9f3r-2vgw-m8xp",
  "modified" : "2026-03-30T14:00:51Z",
  "published" : "2026-03-16T20:45:12Z",
  "aliases" : [ "CVE-2026-32758" ],
  "summary" : "File Browser has an Access Rule Bypass via Path Traversal in Copy/Rename Destination Parameter",
  "details" : "## Description\n\nThe `resourcePatchHandler` in `http/resource.go` validates the destination path against configured access rules before the path is cleaned/normalized. The rules engine (`rules/rules.go`) uses literal string prefix matching (`strings.HasPrefix`) or regex matching against the raw path. The actual file operation (`fileutils.Copy`, `patchAction`) subsequently calls `path.Clean()` which resolves `..` sequences, producing a different effective path than the one validated.\n\nThis allows an authenticated user with Create or Rename permissions to bypass administrator-configured deny rules by including `..` (dot-dot) path traversal sequences in the `destination` query parameter of a PATCH request.\n\n## Steps to Reproduce\n\n### 1. Verify the rule works normally\n\n```bash\n# This should return 403 Forbidden\ncurl -X PATCH \\\n  -H \"X-Auth: <alice_jwt>\" \\\n  \"http://host/api/resources/public/test.txt?action=copy&destination=%2Frestricted%2Fcopied.txt\"\n```\n\n### 2. Exploit the bypass\n\n```bash\n# This should succeed despite the deny rule\ncurl -X PATCH \\\n  -H \"X-Auth: <alice_jwt>\" \\\n  \"http://host/api/resources/public/test.txt?action=copy&destination=%2Fpublic%2F..%2Frestricted%2Fcopied.txt\"\n```\n\n### 3. Result\n\nThe file `test.txt` is copied to `/restricted/copied.txt` despite the deny rule for `/restricted/`.\n\n## Root Cause Analysis\n\nIn `http/resource.go:209-257`:\n\n```go\ndst := r.URL.Query().Get(\"destination\")       // line 212\ndst, err := url.QueryUnescape(dst)             // line 214 — dst contains \"..\"\nif !d.Check(src) || !d.Check(dst) {            // line 215 — CHECK ON UNCLEANED PATH\n    return http.StatusForbidden, nil\n}\n```\n\nIn `rules/rules.go:29-35`:\n\n```go\nfunc (r *Rule) Matches(path string) bool {\n    if r.Regex {\n        return r.Regexp.MatchString(path)      // regex on literal path\n    }\n    return strings.HasPrefix(path, r.Path)     // prefix on literal path\n}\n```\n\nIn `fileutils/copy.go:12-17`:\n\n```go\nfunc Copy(afs afero.Fs, src, dst string, ...) error {\n    if dst = path.Clean(\"/\" + dst); dst == \"\" { // CLEANING HAPPENS HERE, AFTER CHECK\n        return os.ErrNotExist\n    }\n```\n\nThe rules check sees `/public/../restricted/copied.txt` (no match for `/restricted/` prefix).\nThe file operation resolves it to `/restricted/copied.txt` (within the restricted path).\n\n## Secondary Issue\n\nIn the same handler, the error from `url.QueryUnescape` is checked after `d.Check()` runs (lines 214-220), meaning the rules check executes on a potentially malformed string if unescaping fails.\n\n## Impact\n\nAn authenticated user with Copy (Create) or Rename permission can write or move files into any path within their scope that is protected by deny rules. This bypasses both:\n\n- Prefix-based rules: `strings.HasPrefix` on uncleaned path misses the match\n- Regex-based rules: Standard patterns like `^/restricted/.*` fail on uncleaned path\n\nCannot be used to:\n\n- Escape the user's BasePathFs scope (afero prevents this)\n- Read from restricted paths (GET handler uses cleaned `r.URL.Path`)\n\n## Suggested Fix\n\nClean the destination path before the rules check:\n\n```go\ndst, err := url.QueryUnescape(dst)\nif err != nil {\n    return errToStatus(err), err\n}\ndst = path.Clean(\"/\" + dst)\nsrc = path.Clean(\"/\" + src)\nif !d.Check(src) || !d.Check(dst) {\n    return http.StatusForbidden, nil\n}\nif dst == \"/\" || src == \"/\" {\n    return http.StatusForbidden, nil\n}\n```",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/filebrowser/filebrowser/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.62.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.61.2"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/filebrowser/filebrowser/security/advisories/GHSA-9f3r-2vgw-m8xp"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-32758"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/filebrowser/filebrowser/commit/4bd7d69c82163b201a987e99c0c50d7ecc6ee5f1"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/filebrowser/filebrowser"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/filebrowser/filebrowser/releases/tag/v2.62.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22", "CWE-863" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-16T20:45:12Z",
    "nvd_published_at" : "2026-03-20T00:16:17Z"
  }
}