<h3 align="center">
  <code>gform_uploaded_files</code>가 URL에서 <code>../</code>를 허용합니다. 관리자의 삭제 클릭 시 임의 파일 삭제가 발생합니다.
</h3>

<p align="center">
  <a href="https://nvd.nist.gov/vuln/detail/CVE-2026-48866">NVD</a> •
  <a href="https://patchstack.com/database/wordpress/plugin/gravityforms/vulnerability/wordpress-gravity-forms-plugin-2-10-0-1-arbitrary-file-deletion-vulnerability">Patchstack</a> •
  <a href="https://github.com/codewurker/gravityforms/commit/cf2ff65133d581cfed1c308adc1621c3af1f8422">패치된 커밋</a> •
  <a href="https://github.com/codewurker/gravityforms">소스 미러</a>
</p>

---

## 목차

<table>
<tr>
<td width="50%">

**익스플로잇**
- [빠른 시작](#quick-start)
- [작동 방식](#how-it-works)
- [영향](#impact)
- [사용법](#usage)

</td>
<td width="50%">

**방어**
- [기술 심층 분석](#technical-deep-dive)
- [탐지](#detection)
- [수정](#remediation)
- [참고 자료](#references)

</td>
</tr>
</table>

---

## 빠른 시작```
┌─────────────────────────────────────────────────────────────────────┐
│  REQUIREMENTS                                                       │
│  ───────────────────────────────────────────────────────────────    │
│  Target    WordPress + Gravity Forms ≤ 2.10.0.1                     │
│  Form      Public form with a file upload field                     │
│  Python    3.8+ with requests                                       │
│  Auth      None (injection) / Admin creds (trigger)                 │
└─────────────────────────────────────────────────────────────────────┘

---

## 작동 방식

### 공격 흐름```
  ┌───────────────────────────────────────────────────────────────────────┐
  │                        PHASE 1 — INJECTION                           │
  │                    (Unauthenticated — any visitor)                    │
  ├───────────────────────────────────────────────────────────────────────┤
  │                                                                       │
  │   ┌─────────┐    POST gform_uploaded_files     ┌──────────────────┐  │
  │   │ Attacker │ ──────────────────────────────── │  WordPress AJAX  │  │
  │   └─────────┘    {"input_3": [{"url":           │  admin-ajax.php  │  │
  │                   ".../../../../wp-config.php"}] └────────┬─────────┘  │
  │                                                          │            │
  │                  esc_url_raw() → OK (doesn't strip ../)  │            │
  │                  is_valid_url() → OK (../ is valid URL)   │            │
  │                                                          ▼            │
  │                                                 ┌──────────────────┐  │
  │                                                 │   wp_postmeta    │  │
  │                                                 │   (entry stored  │  │
  │                                                 │   WITH ../)      │  │
  │                                                 └────────┬─────────┘  │
  └──────────────────────────────────────────────────────────┼────────────┘
                                                             │
                               ┌─────────────────────────────┘
                               │  (hours, days, or weeks pass...)
                               ▼
  ┌───────────────────────────────────────────────────────────────────────┐
  │                       PHASE 2 — DELETION                             │
  │                 (Admin deletes entry — routine cleanup)               │
  ├───────────────────────────────────────────────────────────────────────┤
  │                                                                       │
  │   ┌─────────┐    delete_entry(42)              ┌──────────────────┐  │
  │   │  Admin  │ ──────────────────────────────── │  Gravity Forms   │  │
  │   └─────────┘                                  └────────┬─────────┘  │
  │                                                          │            │
  │                  get_physical_file_path()                 │            │
  │                  str_replace(url_base → path_base)        │            │
  │                  ../ SURVIVES in the path                 │            │
  │                                                          ▼            │
  │                                                 ┌──────────────────┐  │
  │                                                 │    unlink()      │  │
  │                                                 │                  │  │
  │                                                 │  /var/www/html/  │  │
  │                                                 │  wp-config.php   │  │
  │                                                 │     → DELETED    │  │
  │                                                 └──────────────────┘  │
  └───────────────────────────────────────────────────────────────────────┘

`str_replace()`와 `unlink()` 사이에는 검증이 존재하지 않습니다. 버그는 그 간격에 있습니다.

---

## 영향

<table>
<tr>
<th>대상</th>
<th>영향</th>
<th>심각도</th>
</tr>
<tr>
<td><code>wp-config.php</code></td>
<td>사이트가 오프라인 상태가 됩니다. WordPress가 설치 마법사를 표시합니다. 공격자가 DB를 자신의 서버로 연결하여 <strong>전체 사이트를 장악</strong>합니다.</td>
<td align="center">CRITICAL</td>
</tr>
<tr>
<td><code>.htaccess</code></td>
<td>URL 재작성 및 보안 규칙이 사라집니다. 디렉터리 목록이 열립니다.</td>
<td align="center">HIGH</td>
</tr>
<tr>
<td><code>wp-content/plugins/wordfence/wordfence.php</code></td>
<td>Wordfence WAF가 실행을 중단합니다. 공격자와 사이트 사이에 방화벽이 없습니다.</td>
<td align="center">HIGH</td>
</tr>
<tr>
<td><code>wp-includes/plugin.php</code></td>
<td>플러그인이 로드되지 않습니다. 사이트가 작동을 멈춥니다.</td>
<td align="center">CRITICAL</td>
</tr>
<tr>
<td><code>wp-login.php</code></td>
<td>관리자가 잠겼습니다. 파일을 복원하기 전까지 아무도 로그인할 수 없습니다.</td>
<td align="center">MEDIUM</td>
</tr>
</table>

> *"이와 같은 취약점은 한 번에 수천 개의 웹사이트를 대상으로 하는 대규모 익스플로잇 캠페인에 사용됩니다."*
> [Patchstack Advisory, 2026-06-01](https://patchstack.com/database/wordpress/plugin/gravityforms/vulnerability/wordpress-gravity-forms-plugin-2-10-0-1-arbitrary-file-deletion-vulnerability)

### 삭제 → RCE 에스컬레이션 체인```
  ┌─────────────┐      ┌──────────────────┐      ┌─────────────────┐
  │ Delete       │      │ WordPress shows   │      │ Attacker sets   │
  │ wp-config.php│ ──── │ installer wizard  │ ──── │ own DB creds    │
  └─────────────┘      └──────────────────┘      └────────┬────────┘
                                                           │
                                                           ▼
                                                  ┌─────────────────┐
                                                  │ Full admin      │
                                                  │ access to site  │
                                                  │ (RCE via themes │
                                                  │  /plugin editor)│
                                                  └─────────────────┘

### 예제 시나리오

<details>
<summary><b>시나리오 1: 무음 주입 (관리자 자격 증명 불필요)</b></summary>```bash
python3 poc.py \
  --target https://test.com \
  --form-id 1 \
  --field-id 3

CVE-2026-48866 - Gravity Forms Arbitrary File Deletion
======================================================
Target:     https://test.com
Form ID:    1
Field ID:   3
File:       wp-config.php
Depth:      3
Trigger:    True

---

## 기술 심층 분석

### 호출 스택: 주입 경로```
wp_ajax_nopriv_gform_submit_form                     ← WordPress AJAX, NO AUTH
  └─ GF_Ajax_Handler::submit_form()
      └─ GFAPI::submit_form()
          └─ GFFormDisplay::process_form()
              ├─ GFFormsModel::set_uploaded_files()          [forms_model.php]
              │   └─ esc_url_raw( $file['url'] )             ← does NOT strip ../
              └─ GF_Field_FileUpload::get_value_save_entry() [class-gf-field-fileupload.php]
                  └─ get_multifile_value()
                      ├─ GFCommon::is_valid_url($url)        ← format-only, ../ passes
                      └─ $uploaded_files[] = $file['url']     ← STORED WITH ../

### 취약 버전 vs 패치 버전

<table>
<tr>
<th width="50%">취약 버전 (≤ 2.10.0.1)</th>
<th width="50%">패치 버전 (2.10.1)</th>
</tr>
<tr>
<td>```php
// delete_physical_file() — NO validation
$file_path = self::get_physical_file_path(
    $url, $entry_id
);
$file_path = apply_filters(
    'gform_file_path_pre_delete_file',
    $file_path, $url
);
// ← No check here
if ( file_exists( $file_path ) ) {
    $result = unlink( $file_path );
}

foreach ( $parts as $part ) {
    if ( '.' == $part ) { continue; }
    if ( '..' == $part ) {
        array_pop( $absolutes );
    } else {
        $absolutes[] = $part;
    }
}

$path = implode( DIRECTORY_SEPARATOR, $absolutes );
return str_replace( '|%%protocol%%|', '://', $path );

**`GFCommon::is_file_in_uploads()`** 해결된 경로를 업로드 루트와 비교합니다:```php
public static function is_file_in_uploads( $file ) {
    $file_path = self::get_absolute_path( $file );
    $root_url  = rgar(
        GF_Field_FileUpload::get_file_upload_path_info( '' ), 'url'
    );
    if ( ! str_starts_with( $file_path, $root_url ) ) {
        return false;
    }
    return true;
}

### 호스트: YARA 규칙```yara
rule CVE_2026_48866_Exploit_Payload {
    meta:
        description = "Detects CVE-2026-48866 payload in HTTP POST data or logs"
        cve         = "CVE-2026-48866"
        severity    = "critical"
        author      = "security-research"
    strings:
        $gform_param = "gform_uploaded_files"
        $traversal1  = "../"
        $traversal2  = "..\\"
        $traversal3  = "%2e%2e%2f" nocase
        $traversal4  = "..%2f" nocase
        $url_key     = "\"url\""
    condition:
        $gform_param and $url_key and any of ($traversal*)
}

rule CVE_2026_48866_Vulnerable_Plugin {
    meta:
        description = "Detects vulnerable Gravity Forms lacking is_file_in_uploads fix"
        cve         = "CVE-2026-48866"
        severity    = "high"
    strings:
        $plugin_id = "gravityforms"
        $vuln_func = "delete_physical_file"
        $fix_func  = "is_file_in_uploads"
    condition:
        $plugin_id and $vuln_func and not $fix_func
}

rule CVE_2026_48866_Patched_Plugin {
    meta:
        description = "Confirms Gravity Forms has the is_file_in_uploads patch"
        cve         = "CVE-2026-48866"
        severity    = "informational"
    strings:
        $plugin_id   = "gravityforms"
        $fix_func    = "is_file_in_uploads"
        $fix_helper  = "get_absolute_path"
    condition:
        $plugin_id and $fix_func and $fix_helper
}

| Rule | You Found |
|---|---|
| `CVE_2026_48866_Exploit_Payload` | HTTP 로그 또는 POST 본문에 있는 익스플로잇 페이로드 |
| `CVE_2026_48866_Vulnerable_Plugin` | 수정되지 않은 Gravity Forms 설치 |
| `CVE_2026_48866_Patched_Plugin` | 수정된 Gravity Forms 설치 |

### 로그 분석```bash
# Apache / Nginx access logs — find exploitation attempts
grep -E 'gform_uploaded_files.*(\.\./|%2e%2e)' /var/log/apache2/access.log
grep -E 'gform_uploaded_files.*(\.\./|%2e%2e)' /var/log/nginx/access.log

# Gravity Forms debug log — check for blocked deletions
grep "Not deleting file from URL" /var/www/html/wp-content/uploads/gravity_forms/debug.log

# Verify your install has the fix
grep -r "is_file_in_uploads" /var/www/html/wp-content/plugins/gravityforms/
# → Results in common.php = patched
# → No results = VULNERABLE

| 우선순위 | 작업 | 명령어 |
|---|---|---|
| P0 | Gravity Forms 업데이트 | WordPress admin → Plugins → Update |
| P1 | 패치 확인 | `grep -r "is_file_in_uploads" wp-content/plugins/gravityforms/` |
| P2 | 로그 감사 | `grep -E 'gform_uploaded_files.*\.\./' /var/log/*/access.log` |
| P3 | WAF 규칙 배포 | [Detection](#detection) 섹션 위 참조 |

---

## 면책 조항```
┌─────────────────────────────────────────────────────────────────────────┐
│  LEGAL NOTICE                                                           │
│  ─────────────────────────────────────────────────────────────────────  │
│                                                                         │
│  This tool is provided for AUTHORIZED SECURITY TESTING and EDUCATIONAL  │
│  PURPOSES ONLY. Unauthorized access to computer systems is illegal      │
│  under the Computer Fraud and Abuse Act (CFAA), EU Computer Misuse      │
│  Directive, and equivalent laws worldwide.                              │
│                                                                         │
│  • Always obtain WRITTEN PERMISSION before testing systems you own.    │
│  • You are responsible for complying with all applicable laws.          │
│  • The authors assume NO LIABILITY for misuse of this software.         │
│                                                                         │
│  If you find this vulnerability in production: REPORT IT.               │
│  Patchstack: https://patchstack.com/database/                           │
│                                                                         │
└─────────────────────────────────────────────────────────────────────────┘